Pedro Madureira, an immunologist at the Abel Salazar Institute of Biomedical Sciences at the University of Porto, confirms that in both people vaccinated against Covid-19 and those infected with SARS-CoV-2, cells that produce antibodies are activated and multiply. If, upon second contact with the same pathogen, they again produce these neutralizing molecules. And therefore, It is not important that the same antibodies continue to circulate in the same amount and to maintain protection forever.
In fact, this was not recorded in the history of immunology. it is known that The half-life of antibodies is 23 days – That is, every 23 days, the amount of neutralizing antibodies in the circulation drops to half of what it was. This is “normal, it’s just something that happens” and isn’t necessarily a problem: cells that know how to produce it remain active for years on end, often for life, so some vaccines don’t need to be boosted over time. of human life.
Francisco Antunes confirms these arguments: the latest results from monitoring people infected at the beginning of the epidemic show that The protection offered by circulating antibodies appears to reach levels considered low after one year; That is, even with the risk of reinfection, cases of this type are extremely rare and usually asymptomatic or mild. In other words, cellular immunity continued to ensure that individuals were protected long after infection.
With a vaccine, the same thing is expected to happen. Studies show that people who Developed immune responses to the vaccine maintain this protective ability so far, although it has been nearly a year since the first patients – those who participated in clinical trials – were given. This is also what happens after natural infection: most people who have recovered from SARS-CoV-2 infection are still protected today and it has been 17 months since the first cases appeared in Portugal.
Speaking to the observer, Manuel Carmo Gómez, an epidemiologist at the University of Lisbon’s Faculty of Sciences, noted that Cell immunity appears to persist for at least two to three years; And this, given what is observed in other diseases, can persist for many years. Virologist Pedro Simas, of the Institute of Molecular Medicine, also defended this thesis and puts the longevity of cellular immunity to Covid-19 at five years.
This would rule out the need to revaccinate the population in that time period. But the infectious disease specialist disagrees that this is the case and points to the need to revaccinate the most vulnerable populations — including the elderly, staff with whom they work in nursing homes, health professionals, and people with compromised immune systems — for the upcoming winter. In order to obtain the full effect of immunity, It is essential that the two arms of immunity, the antibody and the cell arm, work simultaneously“If a failure occurs in one of these arms, there is a relative loss of immunity,” he argued.
