Analysis: Seven myths about Covid-19 debunked

16 August 2021

From masks to symptoms and transmission, Professor Christina Pagel (UCL Mathematics) outlines the scientific facts about Covid-19.

I don’t have any symptoms, so even if I have Covid I won’t give it to anyone else

Wrong. People who never get symptoms from Covid are less infectious than people who get symptoms, but they can still have high viral loads and can pass on the virus. And the peak infectiousness in those who do develop symptoms is actually the day or two before they start feeling ill.

Because people who feel fine are far more likely to be out and about than those who are feeling ill, people who have Covid either without symptoms or before they get symptoms contribute a lot to spread. One study estimated people without symptoms are responsible for more than half of new infections.

Do not assume that as long as you feel fine you don’t pose a risk to others. You do!

I won’t pick up or transmit the virus because I’m fully vaccinated

This isn’t true. There have been plenty of documented cases of fully vaccinated people getting Covid, and while the vast majority haven’t needed hospital, many – such as Andrew Marr, for instance – have still felt really rough for a few weeks. We also have proof that vaccinated people can transmit the virus to each other from studies of healthcare workers in India and Vietnam.

The vaccines are incredibly good at protecting you from getting severely ill but less good at preventing you from getting infected. Data from the Imperial REACT study in England suggests that vaccines are somewhere between 50% and 60% effective at preventing infection (regardless of whether you get symptoms).

In the early stages of infection, recent data suggests, vaccinated people have as high viral loads as unvaccinated infected people, but vaccinated people then clear the virus faster.

Vaccination helps prevent both infection and transmission, but it isn’t perfect and you certainly can’t assume that you can’t get sick or that you can’t infect others.

I’ve had Covid already, so I don’t need the vaccine

Having had Covid does give you reasonable protection from being infected again, but it’s not as good as the protection you get from being vaccinated. Immunity from vaccination lasts longer and is more robust to new variants. If you’ve already had Covid then vaccination gives your existing immunity an extra strong boost.

The best immunity we see now is in people who are fully vaccinated after having had Covid. If you’ve recently had Covid, however, you need to wait 28 days after testing positive before getting vaccinated.

I have a good immune system so I don’t need the vaccine

For sure having a good immune system is better than having a bad one, but previously healthy people can still get very sick with Covid, including ending up in hospital and dying. We also know that somewhere between 10% and 30% of adults can end up with long Covid, even with mild initial illness.

And it’s not just about you. You might well get Covid and get over it with no problem, or even have no symptoms at all, but who have you infected? We can all come into contact with vulnerable people in the supermarket, on public transport, visiting family or at the pub. We owe it to them to try to avoid getting infected ourselves.

Children are fine if they get Covid

Children are at much lower risk of getting severely ill or getting long Covid than adults, but can still do so. In England, about one in 200 children with a confirmed case of Covid are hospitalised. Children can also develop what is called multisystem inflammatory syndrome a few weeks after catching Covid, which can be very serious and require intensive care. This is very rare, affecting about 30 children per 100,000 children who get Covid.

Exactly how many children go on to develop long Covid with persistent symptoms is still being investigated, with different studies giving estimates ranging from 2% to 8%. These are lower rates than adults, but they also aren’t zero, and with ongoing high infections in children for the foreseeable future (especially as they remain unvaccinated and return to school), even 2% of a large number is quite high.

Since 19 April there have been more than 420,000 cases in 0- to 19-year-olds in the UK and more than 2,000 hospital admissions in children aged 0-17 with Covid.

Masks don’t work

We now know that Covid is mostly airborne and spread by people breathing, talking, shouting and singing. Masks are by no means perfect, but they do stop lots of your breath hitting someone else’s face when you are interacting with them.

We wear masks primarily to protect others from our breath rather than to protect ourselves from others. If you want to protect both others and yourself, you need a buy a higher-quality mask that fits really well. The best masks are N95, FFP2 or FFP3 ones, which have been shown to be more protective.

A recent study has shown that a high proportion of people wearing masks is associated with a reduction of about 20% in overall population transmission rates, a significant amount.

This wave will be the last …

In the UK there have been headlines calling each of the previous waves the last, and they have been wrong. The government says things are unpredictable and many experts expect infections to rise again as we go into autumn and winter.

Because infections are unlikely to fall to a low level before the next surge, you could argue that it’s all part of the same wave, but the likelihood is that we are in a world of high cases for several months yet. Quite how high, how long and how bumpy the ride will be remains to be seen.

Finally, if a new variant comes along that is more transmissible than Delta or better at infecting vaccinated people, that will change the game once again, just as Delta did in May and Alpha did last December. In this scenario, we would certainly have another, even more severe wave.

We don’t know how likely this, but as long as Covid remains prevalent globally, it will be a possibility for months and potentially years into the future. This is why we can’t definitely say this is the last wave and why it’s so important to help all the world get vaccinated.

This article was first published in The Guardian on 13 August 2021.