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2020-

2020-05-22 e
Viral News - The Illusive Vaccine

Why we might not get a coronavirus vaccine

Politicians have become more cautious about immunisation prospects. They are right to be
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Scientists have worked on coronavirus vaccines before, so are not starting from scratch. Two coronaviruses have caused lethal outbreaks before, namely Sars and Mers, and vaccine research went ahead for both. But none have been licensed, partly because Sars fizzled out and Mers is regional to the Middle East. The lessons learned will help scientists create a vaccine for Sars-CoV-2, but there is still an awful lot to learn about the virus.

A chief concern is that coronaviruses do not tend to trigger long-lasting immunity. About a quarter of common colds are caused by human coronaviruses, but the immune response fades so rapidly that people can become reinfected the next year.

Researchers at Oxford University recently analysed blood from recovered Covid-19 patients and found that levels of IgG antibodies – those responsible for longer-lasting immunity – rose steeply in the first month of infection but then began to fall again.

Last week, scientists at Rockefeller University in New York found that most people who recovered from Covid-19 without going into hospital did not make many killer antibodies against the virus.

“That’s what is particularly challenging,” says Stanley Perlman, a veteran coronavirus researcher at the University of Iowa. “If the natural infection doesn’t give you that much immunity except when it’s a severe infection, what will a vaccine do? It could be better, but we don’t know.” If a vaccine only protects for a year, the virus will be with us for some time.

The genetic stability of the virus matters too. Some viruses, such as influenza, mutate so rapidly that vaccine developers have to release new formulations each year. The rapid evolution of HIV is a major reason we have no vaccine for the disease.

So far, the Sars-CoV-2 coronavirus seems fairly stable, but it is acquiring mutations, as all viruses do. Some genetic changes have been spotted in the virus’s protein “spikes” which are the basis of most vaccines. If the spike protein mutates too much, the antibodies produced by a vaccine will effectively be out of date and might not bind the virus effectively enough to prevent infection. (read more)

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