Two doses of the recombinant zoster vaccine (RZV) are effective against herpes zoster (HZ) for 4 years after vaccination, according to a new study published in the Annals of Internal Medicine.
Findings from the prospective cohort study showed that people who received two doses of the vaccine, regardless of when they received their second dose, experienced 79% vaccine effectiveness (VE) during the first year, with effectiveness decreasing to 73% by year 4. By contrast, the rate of effectiveness during the first year was 70% for people who received a single dose, falling to 52% effectiveness by year 4.
The findings also showed that the rate of effectiveness was 65% for those taking corticosteroids.
The study was conducted between 2018 and 2022 using data from the Vaccine Safety Datalink, a collaboration between the US Centers for Disease Control and Prevention (CDC) and nine healthcare systems across the country.
Researchers evaluated the incidence of HZ, as determined by a diagnosis and prescription for antiviral medication within 7 days of diagnosis, and monitored RZV status over time.
The findings may quell fears that waiting too long for the second dose reduces the effectiveness of the herpes vaccine, according to Nicola Klein, MD, PhD, director of the Vaccine Study Center at Kaiser Permanente in Oakland, California, who led the study.
The long-term efficacy of the vaccine is especially important because older adults are now living much longer than in previous years, according to Alexandra Tien, MD, a family physician at Medical Associates of Rhode Island in Providence.
"People live these days into their 80s and even 90s," Tien said. "That's a large number of years to need protection for, so it's really important to have a long-lasting vaccine."
The CDC currently recommends two doses of RZV separated by 2-6 months for patients aged 50 years and older. Adults older than 19 years who are immunocompromised should receive two doses of RZV separated by 1-2 months, the agency said.
According to Klein, research does not show whether VE for RZV wanes after 4 years. But interim findings from another study following people in clinical trials found VE levels remained high after 7 years.
The risk for HZ increases with age, reaching a lifetime risk of 50% among adults aged 85 years. Complications like postherpetic neuralgia (PHN) characterized by long-term tingling, numbness, and disabling pain at the site of the rash can interfere with the quality of life and ability to function in older adults. The CDC estimates that up to 18% of people with shingles experience PHN, and the risk increases with age.
Just like with any other vaccine, patients sometimes have concerns about the potential side effects of RZV, said Tien. But those effects, such as muscle pain, nausea, and fever, are mild compared to shingles.
"I always tell patients, with any vaccine, immunization is one of the biggest bangs for your buck in healthcare because you're preventing a problem," Tien said.
This study was funded by the CDC through contracts with participating sites. Study authors reported no disclosures. Tien reported no disclosures.
Brittany Vargas is a medicine, mental health, and wellness journalist.
The U.S. is in the thick of another COVID surge, and its likely that youll be exposed to the virus in the coming weeks if you havent been already.
That could be a problem for the large majority of people who have yet to receive the latest bivalent COVID vaccineonly about 19% of adults in the U.S. have opted to get the shot, according to the latest data from the Centers for Disease Control and Prevention (CDC).
Experts say that a close call with COVID can act as the motivation needed to schedule an appointment.
There is no official guidance based on vaccination after coming into contact with someone who then was positive or is positive for COVID-19, said Andrew Stanley Pekosz, PhD, a professor and vice chair of the W. Harry Feinstone Department of Molecular Microbiology & Immunology at the Johns Hopkins Bloomberg School of Public Health. If you havent been boosted, maybe that exposure may be that trigger for you to actually go out and get that vaccine.
Getty Images/Bloomberg Creative
The COVID vaccines work by introducing a segment of protein, or proteins, to the immune system. The vaccines do not infect people with SARS-CoV-2, the virus that causes COVID, but rather help the immune system recognize future exposures.
For about two weeks after a person gets vaccinated, the immune system mounts a response, creating antibodies that recognize unique proteins and store that memory in the immune system. When that person encounters those proteins through a COVID exposure later on, those antibodies know to recognize the virus as an intruder and fight it off.
According to Jesse Bracamonte, DO, a family medicine doctor at Mayo Clinic in Phoenix, Arizona, almost everyones immune system has some recognition of SARS-CoV-2 by now, whether through vaccination or a previous infection or exposure. Because of that, any exposure will likely trigger an immune response. He used the flu as an example.
The body recognizes previous influenza infections, but there are different types of variants now, so your body needs that exact response, he said, noting that previous infection with older variants can cause the immune system to mount some response. However, that response will be much bigger with the latest vaccine, which teaches the immune system to recognize current variants.
If your body is already mounting a response to a COVID exposure, it may be a good idea to wait until you know you arent going to get sick. This period of timefrom exposure to symptom onsetis known as the viruss incubation period. For Omicron variantswhich include the newest JN.1. subvariantstudies have estimated a 23 day incubation period.
Do not get vaccinated if you are testing positive for COVID. Not only will you risk exposing people to the illness, but your immune system will also be at capacity, meaning you wont optimize the vaccines effects, Bracamonte said.
If you are testing negative and choose to get vaccinated right after an exposure, your immune system will begin mounting a response that may protect you from severe illness from this exposure, but it does take about two weeks for the immune system to mount a full response, Pekosz said.
It will certainly protect you in the next two to three months from other exposures, he said.
That must mean youre immune to the virus, right? Unfortunately, not exactly, said Bracamonte.
There are many variables that influence whether a person gets sick, including their stress level, diet, underlying medical issues, the amount of time they were exposed to the virus and the amount of virus a person was shedding when another was exposed.
Each of these variables will be different during each exposure, and not getting infected after one exposure does not mean a person will not benefit from vaccination against future exposures, he said.
According to Bracamonte, people who have underlying medical conditions such as hypertension, obesity, or diabetes, people who are elderly, and those who smoke, should consider getting the latest vaccine if they havent done so.
For people who are young and healthy, you must make that informed decision and have an honest conversation with your physician who you trust. This is unfortunately here to stay, Bracamonte said.
If youve recently had COVID, Bracamonte and Pekosz recommend waiting between three and six months to get vaccinated with the most updated COVID vaccine.
It isnt dangerous to get vaccinated before then, but the idea is to maximize the benefits, and most people retain pretty strong immunity for three to six months after an infection.
Your body is already at maximum in terms of responding to COVID, Pekosz said, adding that waiting for a few months allows the immune systems memory to wane before vaccination ramps it back up, extending protection.
If you havent gotten the latest bivalent vaccineand youve managed to avoid COVID so far this yearIts not too late, Pekosz told Health, noting that the latest vaccine can protect against the emerging JN.1 variant. We expect COVID to be around for the winter season, so take this as a sign to go out and get vaccinated.
A DNA signature might explain why a century-old vaccine rouses the immune system more strongly in some people than in others1.
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doi: https://doi.org/10.1038/d41586-024-00005-y
Sniffling. Coughing. Throat clearing. It seemed to be the soundtrack of this past holiday season.
Maybe it was the festive gatherings. Or the new coronavirus variant. Or the cold weather forcing people indoors.
But the significant spike in cases of COVID-19, flu and RSV that ruined many a familys holiday season in New Jersey continues, even if it finally might be easing in some regions.
Last week, RWJBarnabas Health which operates 12 acute care hospitals in the state saw a significant jump in respiratory illnesses. But a spokeswoman said the number of new patients this week was starting to level off.
Still, many people in the state are falling ill.
An official for Inspira Health, which runs three hospitals in South Jersey, said in a statement that the community of southern New Jersey is seeing a rise in respiratory illness, including COVID, flu, and RSV.
We encourage everyone to take steps to prevent the spread of viral infections wash your hands often, maintain a comfortable distance when interacting with others, wear a mask as appropriate, and stay home when you are not feeling well, said Dr. Tony S. Reed, senior vice president and chief quality, safety and experience officer for the health network, in the statement.
Tens of thousands of people in New Jersey have been sickened by COVID-19 or influenza in recent weeks, and no doubt many more from RSV (respiratory syncytial virus), based just on reported cases. An exponentially higher number of residents probably fell ill in actuality.
Some hospitals in the state have been diverting patients this week due to volume, forced to send the sick to other facilities because they were jammed. For instance, Bayonne Medical Center, Cooper University Hospital in Camden, Inspira Medical Center in Mullica Hill, Toms River Hospital Community Medical Center, Robert Wood Johnson University Hospital Hamilton and Penn Medicine Princeton Medical Center in Plainsboro were all on divert Monday afternoon, according to an online tracker. Cape Regional Health System in Middle Township was also on divert earlier in the day.
In fact, New Jersey saw more than 30,000 COVID-19 cases just over the past month. (As of Tuesday, 1,417 people were hospitalized with COVID-19, with 49 on ventilators. And over roughly the past month, more than 100 people have died from the coronavirus, according to the states dashboard.)
Meanwhile, New Jersey recently had the 10th-highest rate of emergency department visits in the nation for influenza-like illness, according to Beckers Hospital Review. As of Dec. 30, more than 27,000 flu cases were reported in the state.
There have been no flu-related pediatric deaths so far this season in New Jersey, but activity is high in every region of the state. Nationwide, there have been at least 10 million flu cases (although it could be as many as 19 million), according to the Centers for Disease Control and Prevention.
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Spencer Kent may be reached at skent@njadvancemedia.com.
Plant-based and vegetarian diets may play a significant role in reducing the risk of Covid-19, a study has found.
Research, published in the journal BMJ Nutrition Prevention and Health, concluded that the incidence of Covid was 39 per cent lower among people who ate a plant-based diet than among those who ate meat.
The findings highlight the importance of dietary habits in influencing the incidence of infectious diseases.
A team led by Julio Cesar Acosta-Navarro, a professor in the school of medicine at Sao Paulo University, studied a group of 702 volunteers.
"The higher the consumption of plant-based foods, the greater the protection," Dr Acosta-Navarro told The National.
Participants were divided based on their diets between omnivorous and predominantly plant-based.
The latter category consumed more vegetables, legumes, and nuts, and less or no dairy and meat products. They included vegans (who eat no animal products), vegetarians (who consume eggs and dairy products) and flexitarians (who ate meat less than three times a week.)
There were no significant differences in sex, age, or vaccination uptake between the two groups.
However, the plant-based group generally had higher education levels and lower rates of medical conditions and physical inactivity.
Of the total participants, 47 per cent reported having had a Covid-19 infection.
The incidence was notably higher among omnivores (52 per cent) compared to those with plant-based diets (40 per cent).
The duration of symptoms didn't differ significantly between the groups, but omnivores were more likely to experience moderate to severe infections.
After adjusting for factors including weight, pre-existing medical conditions, and physical activity levels, researchers noted no overall difference in symptom severity.
But those following a predominantly plant-based or vegetarian/vegan diet were 39 per cent less likely to become infected than the omnivores, researchers concluded.
"The immune system utilises a range of defense mechanisms to combat infections," Dr Acosta-Navarro said.
"Therefore, it is necessary to have an adequate amount of antioxidant enzymes, vitamins and peptides. Without them the capability of the immune system will be jeopardised.
"Plant-based dietary patterns are rich in antioxidants, phytosterols and polyphenols, which positively affect several cell types implicated in immune function and exhibit direct antiviral properties.
Veganuary
Jimikand ka seekh, a vegan seekh kebab at Punjab Grill. All photos: Chris Whiteoak / The National
"Vegetarians and those on plant-based diets are at reduced risk of chronic diseases of high morbidity and mortality, including ischemic heart disease, Type 2 diabetes, hypertension, certain types of cancer, and obesity, the same conditions that were proved to be risk factor for Covid-19," Dr Acosta-Navarro said.
Shane McAuliffe, senior visiting academic associate at NNEdPro Global Institute for Food, Nutrition and Health who was not involved in the study acknowledged the findings but cautioned that is was an area that warrants more rigorous and high-quality investigation.
Once viewed as a niche lifestyle choice, plant-based and vegetarian diets have gained momentum.
The terminology shift from vegan to plant-based around the mid-2010s marked a significant change in attitudes, broadening the appeal of these diets.
The availability of plant-based options has dramatically improved over the past decade in mainstream grocery stores and restaurants.
Sales of plant-based alternatives to meat and dairy foods surpassed $29 billion in 2020 and are projected to reach $162 billion by 2030.
This represents a significant portion of the global protein foods market.
Major companies, including Kroger, Nestl, and Unilever, are developing plant-based products.
The number of vegans in the US surged from 290,000 in 2004 to almost 10 million in 2019.
The UK saw a 360 per cent increase in vegans over the decade to 2016.
In Portugal, vegetarianism grew by 400 per cent between 2007 and 2017, with laws implemented to offer vegan options in government facilities.
Asian countries including China are also encouraging reduced meat consumption for health and environmental benefits.
Australian food products with vegan claims rose by 92 per cent between 2014 and 2016.
Updated: January 10, 2024, 10:44 AM
Levels of coronavirus in Boston-area waste water have surged in recent weeks, reaching their highest level since the ferocious Omicron surge in the winter of 2021-2022, data from the Massachusetts Water Resources Authority show.
On New Years Day, the seven-day average of coronavirus RNA copies per milliliter of waste water reached 2,743 copies/mL in samples taken from the northern system which includes parts of Boston and communities north of the city and 2,583 copies/mL in samples from the southern system, which includes southern portions of the city and communities to the south.
Those levels are about 10 times higher than early November, and higher than any point since January 2022. Still, its important to note that in terms of waste water levels, the current surge is a small fraction of the Omicron surge two years ago. At that time, levels soared past 11,000 copies/mL in samples before quickly dropping back down.
As home testing has become the norm, waste water readings are an increasingly important way to track the amount of COVID-19 circulating in the community. Waste water testing captures traces of the virus regardless of whether a person was symptomatic or tested for the disease. During past surges, waste water spikes coincided with increases in cases and hospitalizations reported by the state, offering something of an early warning system.
Doctors told the Globe last week that they are indeed seeing more patients with COVID in emergency rooms, and that fewer people are up to date on COVID vaccines. Data from the Massachusetts Public Health Commission shows that COVID-19 is currently responsible for about 6 percent of statewide hospital admissions, up from 2 percent in early November.
Experts told the Globe that staying up to date on vaccines, wearing masks more frequently, and minimizing large indoor gatherings remain good precautions against contracting COVID-19. In addition, its a good idea to take a rapid test if youve been exposed to the virus, even if you dont have any symptoms.
Christina Prignano can be reached at christina.prignano@globe.com. Follow her @cprignano.
The head of the U.N. health agency said Wednesday holiday gatherings and the spread of the most prominent variant globally led to increased transmission of COVID-19 last month.Tedros Adhanom Ghebreyesus said nearly 10,000 deaths were reported in December, while hospital admissions during the month jumped 42% in nearly 50 countries mostly in Europe and the Americas that shared such trend information."Although 10,000 deaths a month is far less than the peak of the pandemic, this level of preventable deaths is not acceptable," the World Health Organization director-general told reporters from its headquarters in Geneva.He said it was certain that cases were on the rise in other places that haven't been reporting, calling on governments to keep up surveillance and provide continued access to treatments and vaccines.Tedros said the JN.1 variant was now the most prominent in the world. It is an omicron variant, so current vaccines should still provide some protection.Maria Van Kerkhove, technical lead at WHO for COVID-19, cited an increase in respiratory diseases across the globe due to the coronavirus but also flu, rhinovirus and pneumonia.We expect those trends to continue into January through the winter months in the northern hemisphere, she said, while noting increases in COVID-19 in the southern hemisphere where it's now summer.While bouts of coughs, sniffling, fever and fatigue in the winter are nothing new, Van Kerkhove said this year in particular, "we are seeing co-circulation of many different types of pathogens.WHO officials recommend that people get vaccinated when possible, wear masks, and make sure indoor areas are well ventilated.The vaccines may not stop you being infected, but the vaccines are certainly reducing significantly your chance of being hospitalized or dying, said Dr. Michael Ryan, head of emergencies at WHO.___The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institutes Science and Educational Media Group. The AP is solely responsible for all content.
The head of the U.N. health agency said Wednesday holiday gatherings and the spread of the most prominent variant globally led to increased transmission of COVID-19 last month.
Tedros Adhanom Ghebreyesus said nearly 10,000 deaths were reported in December, while hospital admissions during the month jumped 42% in nearly 50 countries mostly in Europe and the Americas that shared such trend information.
"Although 10,000 deaths a month is far less than the peak of the pandemic, this level of preventable deaths is not acceptable," the World Health Organization director-general told reporters from its headquarters in Geneva.
He said it was certain that cases were on the rise in other places that haven't been reporting, calling on governments to keep up surveillance and provide continued access to treatments and vaccines.
Tedros said the JN.1 variant was now the most prominent in the world. It is an omicron variant, so current vaccines should still provide some protection.
Maria Van Kerkhove, technical lead at WHO for COVID-19, cited an increase in respiratory diseases across the globe due to the coronavirus but also flu, rhinovirus and pneumonia.
We expect those trends to continue into January through the winter months in the northern hemisphere, she said, while noting increases in COVID-19 in the southern hemisphere where it's now summer.
While bouts of coughs, sniffling, fever and fatigue in the winter are nothing new, Van Kerkhove said this year in particular, "we are seeing co-circulation of many different types of pathogens.
WHO officials recommend that people get vaccinated when possible, wear masks, and make sure indoor areas are well ventilated.
The vaccines may not stop you being infected, but the vaccines are certainly reducing significantly your chance of being hospitalized or dying, said Dr. Michael Ryan, head of emergencies at WHO.
___
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institutes Science and Educational Media Group. The AP is solely responsible for all content.
At the same time, other nasty bugs are circulating. Flu cases are widespread and soaring around the state.
We are certainly seeing a spike in our numbers, said Dr. Marybeth Sexton, an epidemiologist at Emory Clinic about the rise in both flu and COVID cases. We just need to see what happens, whether this calms down as we get farther from the travel people did over the past couple of weeks. Whether we are at a peak or whether we are going to see this perpetuated, I think this will depend on the safety precautions people take.
Older adults and those with weakened immune systems are the most vulnerable to severe illness and complications from COVID. In Georgia, 70% of new COVID hospitalizations during the week that ended Dec. 30 were in those 60 and older.
The COVID virus is constantly changing and a new variant has been spreading rapidly around the nation. The variant, known as JN.1, is a descendent of omicron. It now represents 62% of COVID cases in the U.S. according to the most recent surveillance from the CDC. It makes up about the same share in the eight-state Southeastern region that includes Georgia.
According to the CDC. the continued growth of JN.1 suggests the variant is either more transmissible or better at evading our immune systems. However, there is no evidence JN.1 causes more severe illness. Early lab data indicates that the updated vaccines are still effective against it and continuing to provide protection against severe illnesses. The CDC also said they expect the antiviral Paxlovid to continue to be effective against this variant.
Compared to the first two winters of the pandemic, the state and nation are in a much better place. Fewer people are dying or becoming seriously ill because vaccines and prior infections have bolstered immunity and reduced the severity of illnesses. At least 96% of adults in the U.S. have either been infected by COVID, providing natural immunity, or have been vaccinated. Many fall into both categories.
Omicron variants also dont seem to invade the lungs as much as other coronavirus variants.
Among his patients, Dr. Andrew Reisman, a Gainesville doctor and former president of the Medical Association of Georgia, sees far fewer patients seriously sick compared to the earlier days of the pandemic. In a text, he told The Atlanta Journal-Constitution that encouraging early testing and access to medications to help treat COVID is going a long way in helping his patients tolerate it better.
But COVID remains a threat, especially for those who are older and immunocompromised. Immunity wanes over time. Anyone infected can suffer from long COVID, with sometimes debilitating symptoms that linger for weeks, months or even longer.
The latest preliminary data on weekly COVID deaths in Georgia show 12 COVID deaths for the week ending Dec. 30. Data from early December, which is considered more reliable, shows around 20 COVID deaths a week in Georgia.
Physicians continue to urge everyone, including those not at high risk of severe illness, to get vaccines against COVID and the flu, and to stay home if they become ill.
Sexton said it is certainly reasonable for anyone to consider wearing a mask in public during this wave of illness, and she would strongly recommend masking for those who are high risk, or have someone in their household who is.
Several states have warned of another COVID wave driven by a new variant called JN.1.
New South Wales chief health officer says the variant is partially to blame for the state's "highest level of COVID in a year", while Victoria's health department says the variant has contributed to an "increase in community transmissions along with hospitalisations of COVID cases".
However, experts say so far there has been no evidence that JN.1 is more severe.
So why is it causing more hospitalisations, and what is it doing to case numbers around Australia?
You can think of JN.1 as one of Omicron's many grandchildren. It directly evolved from BA.2.86, the so-called Pirola variant that emerged in August 2023.
Back then,Pirola quickly caught the attention of scientists because it carried 30 spike protein mutations compared to its predecessor, which raised fears that it could better evade our immune systems.
Interestingly JN.1 has just one additional spike protein mutation called L455S but it's a change that makes it more transmissible.
Kirby Institute virologist Stuart Turville said this particular change affected the part of the virus that binds to our cells, helping it to better evade our antibodies.
"[BA.2.86] was dominating in its own way, but it hadn't quite navigated well past the next hurdle, which is actually navigating around antibodies," he said.
"With JN.1, we've got a situation where it's gained the competitiveness of evading antibodies like the XBBs or EG.1."
Research published in the Lancet earlier this month found JN.1 was "significantly" more infectious than BA.2.86.
"These results suggest that JN.1 is one of the most immune-evading variants to date," the researchers from the University of Tokyo wrote.
And while that conclusion was reached after looking at JN.1 in a lab, genomic sequencing data shows the mutation has had real-world consequences.
JN.1 has quickly become dominant in many of the countries it's been detected in; despite only emerging in late 2023, the variant is now responsible for more than half the COVID cases in the United Kingdom, the United States, France, Denmark, and Singapore, according to data from the GISAID variant tracking platform.
In the United States, JN.1 is estimated to make up about 62 per cent of current COVID-19 cases, up from roughly 44 per cent just two weeks ago, the country's Centers for Disease Control said.
It is hard to paint a clear picture of how JN.1 is affecting cases across Australia because comprehensive COVID data has become a thing of the past.
As University of SA epidemiologist Adrian Esterman says, "it is becoming increasingly difficult in Australia to determine the current COVID situation".
"States and territories report at different times (some monthly, some weekly, some not at all), and provide different statistics," he said.
"The only available national collection is not up to date, difficult to use, and often provides no state/territory breakdowns."
Some states and territories have published updates in recent weeks, indicating hospitalisations and/or cases are climbing nationwide.
State
Latest COVID update
Qld
Queensland recorded 1,823 cases in the week to January 1, up from 1,769 cases the previous week. However, there were 2,417 cases recorded in the first week of December. The most recent published update did not include hospitalisation data.
NSW
The Deputy Chief Health Officer this week said about 400 people were being admitted to hospital with COVID-19 each week, and said there was "a high level of COVID activity in the community at the moment".
Vic
An average of 377 people were in hospital with COVID each day in the week to January 2, compared to 307 the week before. The current average is the highest in recent months but remains below the peak in May/June. The seven-day average of ICU patients also increased from 19 to 23.
ACT
The ACT reported 20 cases in hospital in the seven days from December 29, up from 15 admissions in the previous week.
Tas
In the week to January 4 total hospital admissions rose to 53 compared to 45 in the previous week. Two people were admitted to ICU. A total of813 cases were recorded.
SA
Recorded 1,974 cases in the week to January 5, up from 1,475 the previous week. Most recent update did not include hospitalisation data.
WA
There was a decrease in case numbers in the week after Christmas Day which coincided with a drop in PCR tests. However, the weekly hospitalisation average for the state climbed from 162 to 180 and ICU cases rose from five to six.
NT
Stopped publishing COVID-19 data in November 2023.
However, some states' hospitalisation data includes people who were admitted for ailments other than COVID.
Paul Griffin, an infectious diseases physician based in Brisbane, said while Queensland was seeing a higher number of hospitalisations, the cases were on the "lower end of the severity spectrum".
"We're not seeing people in intensive care, and we're seeing very low numbers of people that die from this at the moment which is obviously a good thing," he said.
So JN.1 appears set to start dominating cases globally, and has been blamed for an increase in hospitalisations in Australia.
But is it more severe than other variants? So far, that hasn't been established.
"A couple of recent studies appear to show that JN.1 has a greater affinity for lung cells than previous sub-variants of Omicron, and thus potential to cause a more serious illness," Professor Esterman said.
"However, in the USA where 64 per cent of cases are JN.1, there does not appear to be a major increase in hospitalisations."
Early research presented to the World Health Organization (WHO) last year also indicated that JN.1 was not more severe than other variants, although it said data was limited.
"A study from Belgium in 65-year-old patients has reported no difference in the odds of hospitalisation with JN.1 compared to non-BA.2.86 variants," a WHO report published in December said.
"On the contrary, preliminary data from Singapore indicated lower risk of hospitalisation and severity in BA.2.86 elderly and younger cases."
In its latest update, the US Centers for Disease Control said there was "no evidence that JN.1 causes more severe disease".
So if JN.1 does not cause more severe disease, why are hospital admissions in Australia rising?
The answer comes down to simple maths
"Increased hospitalisations over recent weeks in Australia are most likely due to more cases rather than a more severe strain," Professor Esterman said.
The usual advice for preventing COVID-19 applies: get vaccinated and stay home if you're sick.
Source: Victorian Department of Health
Experts have also highlighted that hundreds of thousands of Australians in a high risk group being over 75 are not up to date with vaccinations.
Data published by the federal government in December showed that only 23 per cent of people over 75 were up to date with their booster shots, and only 30 per cent of aged care residents had been vaccinated in the past six months.
"Most hospitalisations and deaths from COVID-19 in Australia are in elderly people, yet only about 20 per cent are up to date with their booster shots," Professor Esterman said.
"Clearly, it is this group we should be most concerned about."
The experts have also pointed out that even though the latest COVID vaccines target a different variant, XBB.1.5, they will still help protect against serious illness and death from JN.1.
You get the dreaded text: the friend you just met for lunch tested positive for COVID-19. Now youre left to wonder if you, too, will get sick in the coming days.
But when should you expect symptoms to start if you do get sick? The answer has changed from the earliest days of COVID-19, experts say.
In the beginning of the pandemic, we were really looking at seven to 10 days as the window of time where people had to quarantine or isolate after an exposure, says Andrew Pekosz, a virologist at Johns Hopkins University. That has shortened significantly now.
An incubation period is the length of time it takes someone to develop symptoms after exposure to a pathogen. The incubation period for SARS-CoV-2, the virus that causes COVID-19, has shortened considerably since the virus first began circulating, recent data suggest. Incubation periods averaged about five days when the Alpha variant was dominant, about 4.5 days when Beta and Delta were dominant, and about 3.4 days once Omicron took over, according to a 2022 research review.
Newer research from various countries, including Japan, France, and Singapore, also suggests Omicron strains have incubation periods of about three days, or even a little less.
The virus' incubation period is likely shrinking for a few reasons, says Shane Crotty, chief scientific officer at the La Jolla Institute for Immunology. The virus has evolved over time, becoming faster and more adept at infecting humans, Crotty says. Nearly everyone has also now had at least one brush with COVID-19, whether through vaccination or illness. Each encounter leaves behind instructions for the immune system, helping it recognize the virus faster the next time it appears.
You having symptoms is all about your immune system being activated, Crotty explains. The whole pre-symptomatic period is bad news because your immune system has not managed to pull the fire alarm yet. A shorter incubation period means that your body is recognizing the virus faster and pulling those sprinkler systems faster.
Federal health authorities, including the U.S. Centers for Disease Control and Prevention, recommend testing no sooner than five days after a COVID-19 exposure, unless you develop symptoms earlier. But since current variants seem to have incubation periods of around three days, Pekosz says it's appropriate to test as soon as day three, again unless symptoms start earlier.
Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, says he starts to feel more confident he's dodged an infection if hes still feeling healthy three days after a potential exposure. But, "remember, incubation periods are statistical probabilities, he says. Theres always going to be outliers. You could develop a sore throat or runny nose only a couple days after exposure to the virus, or you might not feel sick until day fiveor, if youre lucky, you may not get infected at all.
The timing of symptom onset depends on lots of factors, including the amount of virus to which someone was exposed, Hotez says. Their level of pre-existing immunity may also affect the likelihood or timing of getting sick, Crotty adds.
Given all this variation, Pekosz recommends monitoring your health for up to a week after an exposure and wearing a mask around other people during that time. Remember, too, that false negatives are possible on at-home tests. If you get a negative result, the U.S. Food and Drug Administration recommends taking at least one more test 48 hours later to confirm it.
Its too soon to know exactly, but Hotez says JN.1 is likely to have an incubation period similar to that of other Omicron strains. One 2023 study found that while incubation periods have gotten shorter over time, the various Omicron subvariants have all been similar to one another.
In general, Crotty says, theres a limit to how low incubation periods can go. The SARS-CoV-2 virus works by invading human cells and using them to make numerous copies of itself. SARS-CoV-2 has a long genome that takes a while to copy, so Crotty doubts its incubation period will get much shorter than it already has. Viruses like measles and varicella (which causes chickenpox) on average take longer than a week to incubate, so, by comparison, a three-day incubation period is already pretty fast.
