Natural immunity after a Covid-19 infection can be just as effective as a coronavirus vaccine for a period of at least five months, according to British scientists.
The large SIREN study by the English public health organization Public Health England was conducted on more than 20,000 health professionals.
Based on their preliminary findings, the researchers, led by Dr. Susan Hopkins, who made the relevant post on medRxiv, according to Nature and the Financial Times, concluded that the immune response after an initial Covid infection -19 reduces by 83% the risk of someone getting coronavirus again within the next at least five months.
Study data show that re-infections are very rare, occurring in less than 1% of the 6,614 participants who were already ill with Covid-19. Although the chances are slim, someone who contracted the coronavirus in the first wave of spring could become infected again in the current second pandemic wave.
On the other hand, it has been found that those who are re-infected with the coronavirus may have a high viral load, ie high levels of the virus in their nose and throat, even if they are asymptomatic, making them potentially more contagious to others.
“We now know that most of those who had the coronavirus and developed antibodies are protected from re-infection, but this is not absolute and we do not yet know how long the protection lasts. If someone already has Covid-19 disease, they are unlikely to develop a serious infection again. “But there is still a risk that he will catch the virus again and spread it to others.”
“Re-infection is quite unusual, which is good news. “But that does not mean that one is free to walk around without a mask,” said University of Pennsylvania immunologist John Warry.
The ongoing SIREN, launched in June by British healthcare staff, is the largest coronavirus re-infection study in the world. Participants have blood tests every two to four weeks for antibodies to the SARS-CoV-2 virus, as well as molecular PCR tests to diagnose the coronavirus itself.
Within five months, 44 possible cases of re-infection were found, some of which are still being evaluated. Only 30% of the 44 people with a possible re-infection had symptoms, compared with 78% of those who had been infected for the first time.
At present, researchers do not have enough evidence to suggest who may be more at risk for a recurrent infection. For immunity acquired through vaccination, the study will have more data later in the year.
The study will also collect more long-term data to shed light on the question of how long natural immunity lasts, but also to what extent it protects against newer, more contagious coronavirus strains, such as the “British” B.1.1 mutation. .7. Greek-born immunologist George Cassiotis of the Creek Research Institute in London said “this is another open question”, as it is possible that the immune response to one strain of the virus is less effective than another variant.
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