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Covid-19: Can I get infected for the second time? No immunity?


With the Covid-19 pandemic infecting more than half a million people globally, virologist Guido Vanham, the former head of virology at the Institute for Tropical Medicine in Antwerp, Belgium, talks about the less understood novel coronavirus

He maintains that the new coronavirus belongs to a different virus family than the influenza viruses, making the available flu vaccines and medications ineffective against it. However, it is quite similar - up to 95% - to the Sars virus, and that may offer a glimmer of hope in that the world could have a realistic perspective on a vaccine in six months, with a generous dose of luck.

Vanham also hazards a guess on if weather changes -- the onset of summer in particular -- will have any impact on the potency of the virus. He explains the possible reasons why this virus is more infectious than the Sars Cov1 and the Sars Cov2 viruses even though its genetic composition is quite similar to those. And, unlike flu and other infections, a once-infected and recovered person doesn't necessarily get immunity against the virus - at least there is no evidence so far to suggest this.

Excerpts from the Q&A on Weforum.org, which was originally published by Novaya Gazeta.

Could you summarise the facts that we know about the virus for sure? Covid-19 is a completely different virus from the Influenza viruses which belong to a very different group, meaning that flu vaccine or flu medication will not help. For now, we have no medication or vaccine for the virus.

It resembles very much the Sars virus which emerged in 2003 and less closely to another virus which emerged a few years later - the Mers virus

The present virus, Covid-19, is more infectious and is mainly transmitted via aerosols (from people who cough or sneeze, etc.), but you can also get it by contact with objects that infected people, who are not necessarily sick, have touched.

Can we explain why it is so infectious? No, that is a matter of research. Remarkably, the previous Sars Cov1 and the present Sars CoV2 use the same "receptor" for entry in cells and the suggestion is that the "envelope proteins" of the present Sars CoV2 are just more efficient in using the "entry door" into the lung cells and elsewhere in the body.

Why elderly are more at risk? I cannot give you a final answer to that but this is not so uncommon. Children's immune systems react in a less vigorous (in this case also more appropriate) way and they don't get that sick. While the immune system of adults sometimes overreacts to those viruses and that makes them sick.

Asymptomatic patients can also infect others. Isn't this common for all viruses? Indeed, most other viruses have this characteristic but the proportion of people who can transmit the virus without symptoms is different for different viruses. For Covid-19, we have no exact numbers yet.

Do those infected become immune to Covid-19? Currently, there is no evidence that those infected and recovered will become immune to the novel coronavirus. Also, there is a suggestion that they can become susceptible again after a short period of time.

"Herd immunity" requires a large proportion of the population to first get infected, overcome the infection and then maintain sufficient levels of antibodies to not get infected again. And in this case, the virus mutates and can overcome the herd immunity, much like Influenza does.

Is social distancing the current option? And wait for the treatment or vaccine? Yes, but it's doubtful that treatment will be available within weeks. The more likely scenario is that this epidemic will continue and will end at some point. Taking example of China where according to the official numbers, there are no new "endogenous" infections and the epidemic looks to be over. China took very strict measures and even prevented people from leaving their homes.

Should we stay home forever? No, we shouldn't. Today, I went out. We keep a distance and we don't gather more than three people - that is forbidden.

Will the virus start to slow down owing to natural factor (summer or whatever else), as happened with Sars? That is a possibility. The other point is that for every virus, not every human is equally susceptible. There are always people in a population who are more or less susceptible to a certain virus.

The US has already announced testing of a vaccine. How long should it take? There is a lot of technology available, different platforms to use, but in the end, you cannot predict [how long it will take.

Also, animal viruses related to coronaviruses (the feline enteric coronavirus, for example), can be fatal as it happened in the case of vaccinated cats which got an even more severe infection.

But again, we cannot predict - it could be as simple as the measles vaccine. I, along with you and everybody else on earth, do hope so.

What is the most probable scenario for the vaccine?

This Covid virus is closely related to the Sars virus, up to 95 per cent, so maybe the possibility for the virus to change (its "genetic space") is not that large.

At present, in vitro tests have suggested antibodies for Sars could neutralise this virus so it is possible maybe in half a year's time we will have a realistic perspective on a vaccine. But, as I just explained, there are risks that should be taken into account.

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