Covid-19: A study by researchers at the University of Padua, Italy, and Imperial College London showed that antibodies against covid-19 last for at least nine months in the body of those who had the infection. The findings were published in the scientific journal Nature Communications on July 19th.
More than 85% of the 3,000 residents of Vo’, an Italian community in the Veneto region, were tested for infection with SARS-CoV-2 — the virus that causes covid-19 — between February and March 2020. Then they were tested again in May and November 2020 for antibodies to the virus. 98.8% of people infected between February and March still had detectable levels of antibodies in November — and there was no difference between people who developed symptoms and those who were asymptomatic (without any symptoms of the disease).
The participants’ antibody levels were monitored using three assays — tests that detect different types of antibodies, which respond to different parts of the virus. The results showed that, although all types of antibodies suffered some decline between May and November, they remained active.
The team also found cases of increased antibody levels in some people — suggesting potential reinfections with the virus, which stimulates the immune system.
“We found 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,” said the study’s lead author, scientist Ilaria Dorigatti, from the Center of Global Infectious Disease Analyzes and the Abdul Latif Jameel Institute (J-IDEA) at Imperial College.
“However, our study shows that antibody levels vary, sometimes markedly, depending on the test used. This means that care must be taken when comparing estimates of infection levels in a population obtained in different parts of the world with different tests and at different times,” said the researcher.
Professor Enrico Lavezzo, from the University of Padua, said tests in May showed that 3.5% of the Vo’ population had been exposed to the virus, although not everyone was aware of the exposure, given the high number of asymptomatic people. “However, at follow-up, done about nine months after the outbreak, we found that the antibodies were less abundant, so we need to keep monitoring the persistence of antibodies for longer periods of time,” he said.