Covid-19 antibodies last for at least six months after infection for the majority of people who have had the virus, new research has found.
The study also found that almost nine per cent of the UK population had been infected by December 2020, with the rate as high as 12.4 per cent in London and as low as 5.5 per cent in Scotland.
Do antibodies provide immunity?
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The study, from UK Biobank, the UK’s major biomedical database and research source, measured the levels of previous coronavirus infections in various population groups across the country, and looked at how long antibodies persisted in those who were infected.
From the end of May 2020 to the beginning of December 2020, researchers collected monthly blood samples and data on potential symptoms from 20,200 UK Biobank participants, as well as their adult children and grandchildren.
A total of 99 per cent of participants who had tested positive for previous infection were found to retain coronavirus antibodies for three months after being infected, while 88 per cent retained antibodies for the full six months of the study.
The findings suggest that antibodies produced following natural infection may provide a degree of protection for most people, preventing them from becoming infected a second time for at least six months.
However, scientists say it is still unclear as to how this relates to immunity and further research is needed to determine how long protection may last.
Professor Naomi Allen, UK Biobank chief scientist, explained: “This important study has revealed that the vast majority of people retain detectable antibodies for at least six months after infection with the coronavirus.
“Although we cannot be certain how this relates to immunity, the results suggest that people may be protected against subsequent infection for at least six months following natural infection.
“More prolonged follow-up will allow us to determine how long such protection is likely to last.”
Health Minister Lord Bethell cautioned that, while the findings offer some promise, it is still vital that people remain at home, even if they have had Covid-19, as further research is needed to fully understand how long antibodies will provide protection.
Can antibodies prevent transmission?
The study also found that the proportion of the population with antibodies to coronavirus (seroprevalence, which indicates past infection) rose from 6.6 per cent at the start of the research period, to 8.8 per cent by the end.
While there was no difference in seroprevalence by gender, the proportion of participants with detectable antibodies was found to be highest in younger people (13.5 per cent among those under 30) and lowest in the elderly (6.7 per cent among those over 70).
The seroprevalence of coronavirus was highest among participants of black ethnicity (16.3 per cent) and lowest among those of white (8.5 per cent) and Chinese ethnicities (7.5 per cent).
The most common symptom associated with having coronavirus antibodies was a loss of sense of taste and smell, which was reported by 43 per cent of sero-positive participants.
Around one quarter (24 per cent) of sero-positive participants were completely asymptomatic, and 40 per cent did not have one of the three most common Covid-19 symptoms - fever, persistent dry cough, or loss of sense of taste or smell.
However, researchers warned that just because people built up an antibody response, it does not mean they cannot still pass the virus on to others.
Professor Sir Rory Collins, UK Biobank principal investigator, said: “Both with vaccines and indeed with past infection, we don’t yet know what impact that has on the ability to be carrying the virus and transmitting to others.
“So I think one important message both for people who have been infected, and for people being vaccinated, is you may be protected, to some extent, but you may still put others at risk.
“So it’s important to maintain the social distancing and the lockdown measures in line with the government guidance.”
Sir Rory added that the findings support the Government’s decision to delay the second dose of Covid-19 vaccines for up to 12 weeks.
He said: “The fact that infection is producing antibody response that lasts a long time, and as we’ve seen in other studies, is protecting against reinfection does support the government’s decision to delay the second dose.
“And the evidence that they have from the antibody studies that were done with vaccines I think supports the delay, which then allows first doses to be given to very much large numbers of people, which was part of the rationale for the government.”