What we know and don’t know about Covid-19 – BBC News

The virus affects people differently

As well as age differences, it emerged that the virus affected men more seriously than women, and some racial groups were more vulnerable than others. Some people also have a kind of mysterious hidden immunity, which they may have acquired long before the pandemic began.

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The virus can damage organs

Though Covid-19 is a respiratory virus, it doesn't limit itself to damaging the lungs. Now scientists know that it can infect the cells that line blood vessels and affect a range of other important organs, such as the heart, brain, kidneys, liver, pancreas and spleen. The effect has been found even in young, low-risk people. No one knows how long the impairments will last, or whether they will ever fully resolve.

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The virus spreads exponentially

...but most people don't understand that. A spate of studies have shown that people who are susceptible to this "exponential growth bias" are less concerned about Covid-19's spread, and less likely to endorse measures like social distancing, hand washing or mask wearing.

Read more the psychology underlying our response to the threat posed by the pandemic:

Coronavirus vaccines are safe and effective

Vaccine scientists moved extraordinarily fast, under extraordinary pressure. With the weight of global expectation, they have delivered safe, effective vaccines that had been rigorously tested in trials. BBC Future got first-hand experience when one of our journalists volunteered to participate in the Oxford-Astrazeneca trial (and he's still doing his weekly swabs, months later).

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A single dose of vaccine provides moderate protection

But it comes with some important caveats. The extent of protection depends on the vaccine in some cases, there isn't enough data to be sure of any just yet. Until you receive a booster dose and many more people are vaccinated, it's vital to continue social distancing, wearing a mask and following other public health advice. In fact, it's helpful to imagine that it didn't happen.

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Herd immunity usually happens via vaccines

Herd immunity is a kind of disease resistance that occurs within a population, as a result of the build-up of immunity in individuals. But contrary to the impression you might have got during the pandemic, there are many reasons that it is not normally achieved by intentionally allowing a virus to spread. Many scientists now believe that any attempt to do so would have led to unacceptable levels of deaths. But herd immunity can also be acquired via vaccines, which lead to significantly less collateral damage and may provide superior protection to natural infections.

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Most vaccines probably won't prevent transmission

That said, the current Covid-19 vaccines weren't judged on their ability to prevent the spread of the virus instead, they were assessed by their ability to prevent people from developing symptoms and falling ill. Research on whether the vaccines will also prevent transmission of the virus is still ongoing, but there are some early indications that both the Pfizer-BioNTech vaccine and the Oxford-Astrazeneca vaccine can reduce transmission. There are some early hints that other vaccines may be able to stop it entirely.

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Death rates vary from country to country

and there are many reasons why, to do with the way deaths are counted. One outcome of this is that it can be difficult to compare death rates in different countries. Far from being unique to Covid-19, such differences in the way deaths are counted are common when an epidemic occurs.

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What we know and don't know about Covid-19 - BBC News