Covid: immunity from a vaccine could disappear after a few months?

20-07-2020 by Mirai

British researchers have analyzed the immunity of patients affected by Covid-19. They found that the level of antibodies decreased after three months.

The scientific community continues to seek a vaccine or treatment against Covid-19. The issue of immunity also arises regularly. A new British study published in the pre-publication scientific journal MedRxiv suggests that antibodies from infected patients decrease or even disappear after a few months.

To find out, researchers at King's College London (UK) analyzed the immune response of 90 patients and healthcare professionals from the Guy and St Thomas NHS Foundation Trust who were affected by Covid-19.

While 60% of volunteers had developed strong antibodies in response to infection, the researchers found that only 17% of patients retained the same level of antibodies three months later.

Therefore, these results suggest that the antibodies would have a limited lifespan and that patients already affected by Covid-19 could therefore be re-infected. A finding that once again questions the idea of potential collective immunity.

Covid-19: even shorter immunity in asymptomatic patients

Another study published in June 2020 in the journal Nature Medicine and conducted by Chinese researchers has already suggested that the immune response in patients infected with the virus decreased a few weeks after recovery.

To find out, the researchers followed 37 asymptomatic patients tested by PCR, a sample of nasal cells with a swab. From 8 to 75 years, 22 of the participants were women and 15 men. All had been hospitalized in Wanzhou province (China) and placed in isolation. Scientists at Chongqing University of Medicine noted that the median time for virus shedding was 19 days for them, compared to 14 days for symptomatic patients.

To study the immune response of these two groups, the researchers compared asymptomatic subjects with 37 people infected with Covid-19 and who had exhibited symptoms. Eight weeks after the start of the infection, they found that the level of antibodies had decreased by 81.1% in asymptomatic people. As for the symptomatic, their immune response was reduced by 62.2%.

For scientists, immunity against mild forms could last "from a few weeks to a few months." After this period, subjects should be retested to see if the antibodies persist over time.