COVID-19 Antibodies Persist For At Least Nine Months After Infection | Imperial News

Tests of an entire Italian city show antibody levels remain high nine months after infection with SARS-CoV-2, whether symptomatic or asymptomatic.

Researchers at the University of Padua and Imperial College London tested more than 85% of the 3,000 residents of Vo ‘, Italy, in February / March 2020 for infection with SARS-CoV-2, the virus which causes COVID-19, and tested them again in May and November 2020 for antibodies to the virus.

The strength of the immune response does not depend on the symptoms and severity of the infection Dr Ilaria Dorigatti

The team found that 98.8% of people infected in February / March had detectable levels of antibodies in November, and that there was no difference between people who had shown symptoms of COVID-19 and those who had not presented any. The results are published today in Nature Communication.

Antibody levels were monitored using three “tests” – tests that detect different types of antibodies that respond to different parts of the virus. The results showed that although all types of antibodies showed some decline between May and November, the rate of degradation was different depending on the assay.

The team also found cases of increased antibody levels in some people, suggesting potential re-infections with the virus, boosting the immune system.

Antibody Levels

Lead author Dr Ilaria Dorigatti of the MRC Center for Global Infectious Disease Analysis and the Imperial’s Abdul Latif Jameel Institute for Disease and Emergency Analytics (J-IDEA) said: no evidence that antibody levels between symptomatic and asymptomatic infections differ significantly, suggesting that the strength of the immune response does not depend on the symptoms and severity of the infection.

“However, our study shows that antibody levels vary, sometimes markedly, depending on the test used. This means that caution is required when comparing estimates of infection levels in a population obtained from different parts. of the world with different tests and at different times. “

Professor Enrico Lavezzo, University of Padua, said: “The tests in May showed that 3.5% of the Vo ‘population had been exposed to the virus, although not all of these subjects were aware of the virus. their exposure given the large fraction of asymptomatic infections.

“However, during the follow-up, which was done about nine months after the outbreak, we found that the antibodies were less abundant, so we must continue to monitor the persistence of the antibodies for longer periods.”

Subsequent infections

The team also studied the infection status of household members, in order to estimate the likelihood that an infected member would transmit the infection within the household. Their modeling suggests that there was a probability of approximately 1 in 4 that a person infected with SARS-CoV-2 would transmit the infection to a family member and that most transmissions (79%) were caused by 20% of infections.

This finding confirms that there are large differences in the number of secondary cases generated by those infected, with the majority of infections no longer generating infections and a minority of infections generating a large number of infections.

The large differences in how an infected person can infect others in the population suggest that behavioral factors are essential for epidemic control, and physical distancing, as well as limiting the number of contacts and port. masks continue to be important in reducing the risk of disease transmission, even in highly vaccinated populations.

Control measures

The team’s dataset, which includes the results of two mass PCR testing campaigns conducted in February and March and the antibody survey conducted in May and then again in November, also enabled them to distinguish l ‘impact of various control measures.

They showed that without case isolation and short-term lockdowns, manual contact tracing alone would not have been enough to suppress the outbreak.

Prof. Andrea Crisanti, Project Manager, Imperial Life Sciences Department and University of Padua Molecular Medicine Department, said: “Our study also shows that manual contact tracing – research of positive individuals on the basis of known and declared contact data – would have had a limited impact on the containment of the epidemic, if it had not been accompanied by mass screening.

Dr Dorigatti added: “It is clear that the epidemic is not over, neither in Italy nor abroad. In the future, I think it is of fundamental importance to continue to administer the first and second doses of vaccine as well as to strengthen surveillance, including contact tracing. Encouraging caution and limiting the risk of contracting SARS-CoV-2 will remain essential. “

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“Dynamics of anti-SARS-CoV-2 antibodies and transmission from serological tests at the community level in the Italian municipality of Vo” by Ilaria Dorigatti et al. is published in Nature Communication.