The new Covid-19 vaccine may give people immunity from the disease for 90 days, or three months.
A paper published by the New and Emerging Respiratory Virus Threats Advisory Group said that the duration of the jab’s effectiveness is “not yet fully understood”.
Their estimate is based on the fact that other coronaviruses tend to reinfect after one or two years, the Mirror reports.
Scientists wrote: “Based on the variability in the data and differential responses in the population we conservatively estimate that a protective immune response after SARS-CoV-2 infection or vaccination may last for 90 days.”
Reinfections with seasonal coronaviruses occur frequently at 12 months and sometimes as early as six months – but not within three months – scientists said.
They explained: “Based on this information, we conclude that: Within one month of natural infection, a high proportion of people will develop immunity which is protective against disease caused by reinfection.
According to the paper, new tests suggest the presence of antibodies in people who have been infected ‘approached 100 percent’. They can be measured within about a week of symptoms developing, peaking after about a month, and then declining to a ‘quite stable level which shows little evidence of further decline over five or six months’, it added.
However, the scientists acknowledged that despite the apparent persistence of antibodies, the length of immunity after either infection or vaccination is currently not well-understood.
The scientists wrote: ‘We conservatively estimate that a protective immune response after SARS-CoV-2 infection or vaccination may last for 90 days (moderate confidence). ‘Based on this information, we conclude that: Within one month of natural infection, a high proportion of people will develop immunity which is protective against disease caused by reinfection.
‘This protection is likely to persist for at least three months.’
Experts added that a small proportion of people may not develop immunity following either natural infection or vaccination – but the number is said to be small compared to the majority who get immunity.
According to NERVTAG, “natural immunity is sustained in most cases”.
The document added that coronavirus antibodies can be detected in at least 90% of people who have been infected with the virus – and this figure approaches 100% with new tests.
The antibodies can be measured within about a week of symptoms developing, the paper added.
The document, which was published on Friday, was considered by SAGE on November 19.
Scientists said the trials of coronavirus vaccines “suggest that a high degree of immunity to Covid-19 disease can be obtained, at least in the short-term.”
Despite some uncertainties around the level and duration of immunity, experts concluded: “Some form of Covid-19 immunity certification is likely to be possible but further data and considerations are needed before a recommendation can be made.”
