What a study on people healed in Vo ’Euganeo says about immunity from Covid-19

After 9 months of infection, antibodies against the coronavirus are present in 98.8 of the recovered. And this also applies to asymptomatic people

The president of the Veneto Region, Luca Zaia, in Vo 'Euganeo (Roberto Silvino / Ipa) How long does the protection against Covid-19 provided by antibodies last for those who have had the infection and how long 'has exceeded? Definitely 9 months. Maybe even more, but we don't know yet. This is confirmed by a new study, conducted by the University of Padua, together with Imperial College London, and coordinated by virologist Andrea Crisanti. The investigation, carried out in Vo 'Euganeo, the first Veneto epicenter of the epidemic, shows that after 9 months from the encounter with the virus, almost all of the recovered (former Covid patients) have specific antibodies against Sars-Cov-2, a important part of the immune response, still at high levels. The research, published in Nature Communications, does not in any way indicate that healed people can stop following protective rules or risk being infected, perhaps by new variants of the virus.

Monitoring with serological tests

The municipality of Vo 'Euganeo, strongly affected by the epidemic, is back in the spotlight with a study - not the first carried out here during the pandemic - on immune response of the local population. The researchers carried out sweep and repeated serological tests on more than three quarters of the approximately 3 thousand inhabitants of Vo ', some of whom in February and March 2020 contracted Covid-19, both in severe and mild form or without symptoms. As of November 2020, 98.8% of these people had antibodies to the coronavirus at detectable and significant levels. The result is valid for both symptomatic and asymptomatic cases. There have also been cases in which the levels of antibodies increased over time, a result that is probably the result of re-infections, therefore new encounters of the virus, which have enhanced the activation of the immune system.

The rules for the recovered

The question of the duration of the immune response, both in the vaccinated who have never encountered the pathogen and in the recovered, has long been at the center of the health debate. Being able to answer is important to better understand how many doses the convalescents will have to receive and when it is good to administer the vaccinations. The guidelines currently recommend providing vaccination at least three months but no later than six. Furthermore, since March, a circular from the Ministry of Health has indicated that it is possible to administer only one dose of vaccine for those who have had Covid-19. There are no new indications, although this test - together with others - could help to have more information on the duration of immunity.

From how the infections occurred to contact tracing

Lo study goes beyond the question of the healed and focuses on the methods of contagion and the effectiveness of some of the measures adopted to contain it. In particular, about one in 4 positive people has transmitted the infection to a family member. According to these data (which concern Vo 'but which could in part be generalized) and by reconstructing the chains of infections, most people have not transmitted the virus to others, and a few primary cases are the basis of all secondary infections. The result provides further evidence of the importance of isolation for positives and other norms - masks, distance, hand washing - to defend themselves.

Also, where preventive isolation has not been possible of cases and in the absence of lockdown, manual contact tracing (traditional tracking, asking the patient to list contacts) was not sufficient to prevent the spread of cases. According to the study, the manual search for positive cases, comments Crisanti, appears to have a limited impact if not accompanied by mass screening. Another reason why active and continuous monitoring, contact tracing and the ability to sequence the virus are important weapons even in this phase in which new variants seem to be increasingly the masters.


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