The level of natural immunity people acquire from having caught the CCP virus in the past is high and likely to be roughly the same as the protection they would get from vaccination against the disease, scientists have said, a new official study shows.
Public Health England (PHE) said in a media release on Jan. 14 that its SIREN study of 20,787 health care workers concluded that having previously had the disease gave people at least 83 percent, but up to 99 percent, immunity to reinfection probably for a minimum of five months.
Professor Susan Hopkins, Senior Medical Advisor at PHE and the SIREN study lead said, “This study has given us the clearest picture to date of the nature of antibody protection against COVID-19.”
‘Protected From Reinfection’
“We now know that most of those who have had the virus and developed antibodies, are protected from reinfection,” she said.
Though the study didn’t include research on people who had received vaccines, scientists welcoming its findings said it shows that previously infected people gain as much immunity from having caught the disease in the past as they will get from a vaccine.
“The take-home message from this study is that a primary infection with SARS-CoV-2 provides at least 94 percent protection against symptomatic reinfection for at least 5 months,” Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh said.
“This suggests that natural infection provides short term protection against COVID-19 that is very similar to that conferred by vaccination.”
Meanwhile, Lawrence Young, virologist and professor of molecular oncology at Warwick Medical School, echoed the inference and said the SIREN findings bore out the results of earlier studies.
“Overall, this study supports previous observations from around the world which have shown that infection with SARS-CoV-2 provides a high degree of immunity to repeat infection, at least in the short to medium term,” he said.
‘Similar’ to ‘Licenced Vaccines’
“The study also indicates, along with previous work, that primary infection offers similar levels of protection from symptomatic infection as the currently licensed vaccines,” he added.
The SIREN study findings are based on data from regularly testing the 20,787 health care workers for new infections of the CCP virus, as well as for antibodies indicating prior infection, over six months since June last year.
The conclusion that a high percentage of immunity was afforded by having already had the virus was drawn by researchers when they found that potential reinfections had occurred in just 44 people out of the 6,614 who had tested positive for antibodies.
Despite the reassurances the research offers, due to remaining transmission risks and not yet knowing exactly how long immunity lasts, Professor Hopkins urged caution and said people should still stick to the stringent stay-at-home restrictions that have been in place since Jan. 5 in the UK’s third national lockdown.
“We now know that most of those who have had the virus and developed antibodies are protected from reinfection, but this is not total and we do not yet know how long protection lasts,” she said.
“Crucially, we believe people may still be able to pass the virus on.”
Professor Riley echoed Hopkins’ warning. She said that though the research suggested that people who had recovered from the CCP virus are “much less likely to transmit it to others,” some reinfected people, even those without symptoms, could still pass it on.
“So you cannot assume that just because you have had the virus before that you can’t be infectious,” she said.
“These data reinforce the message that, for the time being, everyone should consider themselves to be a potential source of infection for others and should behave accordingly.”
The SIREN study covers a period before the extensive spread of a new variant of the disease that originally proliferated in the Southeast of England.
SIREN researchers will continue the study for another year, PHE said, to further investigate exactly how long immunity lasts, how effective vaccines are, and to what extent immune people carry and pass on the disease.
Over two and a half million people in the UK have thus far received an initial jab of vaccine. The government’s target is that 15 million should receive their first dose by Feb. 15.