Since the start of the Covid-19 epidemic, many researchers have questioned the lifespan of antibodies after infection with the coronavirus. It is now possible to see more clearly. UK BioBank, a UK biomedical database and research resource, released the results of a study on the duration of immunity conferred after infection with Covid-19 on February 3.
88% of infected people would retain antibodies six months after infection with Covid-19
To carry out the study, British scientists collected blood samples from around 20,200 people between May 27 and December 4, 2020, or over six months. Their aim was to measure the levels of infection in various population groups in the UK and to determine the duration of antibodies in people who have contracted the disease. A total of 1,699 individuals exhibited antibodies.
The results of the study revealed that 99% of patients, who had tested positive for a previous infection, retained antibodies against Covid-19 for three months. Other data: 88% of those infected had antibodies throughout the study, ie for six months.
"This finding indicates that antibodies produced following natural infection, and potentially following vaccination, can protect most people from subsequent infection for at least 6 months," can we read in the works.
Covid-19: 5 people affected by a second infection
The conclusions of this English study echo those of work published in the scientific journal Clinical Infectious Diseases. A team from the Toulouse University Hospital virology laboratory also conducted a study on the rate of protection and life expectancy of neutralizing antibodies.
For the purposes of the study, the researchers carried out serological tests on 8,700 healthcare staff at the Toulouse University Hospital in June / July 2020. Results: 276 people were affected by the coronavirus. Scientists then sought to detect the presence of antibodies made by the body to fight the infection. "We put them to neutralization, we looked for the presence of neutralizing antibodies against SARS-CoV-2. This was the case, in over 95% of cases ", detailed Chloé Dimeglio, principal author and biostatistician in the virology laboratory of the Toulouse University Hospital in 20 minutes.
From November 30 to December 9, 2020, new serological tests were performed on the participants. The researchers found 1,028 new infections among the 8,482 volunteers diagnosed negative during the summer. They also observed five new cases of reinfection in the 276 patients already infected with the coronavirus.
"It's not huge, it corresponds to a rate of 1.8%. There was no link between the fact of having reinfected and the level of neutralizing antibodies, that is to say that there were re-infections with high rates and low rates ", specified the researcher to our colleagues from 20 minutes. According to scientists, infected patients were never hospitalized during the first two waves.
A weaker natural immunity than that guaranteed by vaccination
After six months of follow-up, the Toulouse University Hospital team indicated that the majority of neutralizing antibodies were either stable or increasing (96.7%) in patients infected with the virus. In December 2020, researchers estimated the protection rate by comparing the infection rate of negative cases and the reinfection rate of positive cases detected during the summer. "This shows that having contracted a first infection with Sars-Cov-2 induces protection of around 84.8%: when you contracted a first infection (six months previously), you have 84.8% lucky not to contract it ", explained Chloe Dimeglio.
In their study, however, the researchers stressed that the rate of protection after a first infection is lower than that guaranteed by vaccination. In particular, Pfizer and Moderna vaccines provide 95% immunity. According to the Toulouse University Hospital team, people already infected with the coronavirus should also be vaccinated to protect themselves from further contamination.
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