The number of anti-covid antibodies decreases both in previously infected patients and in vaccinated people, land performance, however, only improves for antibodies developed after infection and not for those after vaccination. This is what emerges from a study conducted by Carmit Cohen of the Sheba Medical Center in Ramat Gan, Israel, and colleagues. According to experts, having Covid infection potentially provides long-term protection. And it might explain why the recovered appear to be better ‘equipped’ against a new infection than those who have only been vaccinated. The scientists also found that, contrary to what was expected, previously infected patients with obesity had a higher and more sustained immune response than overweight and normal weight patients.
While protection against reinfection lasts a long time in people who have had Covid, so-called ‘breakthrough’ infections (those that breach the vaccine shield) are increasingly common 6 months after the vaccine. In this study, the authors analyzed the humoral (antibody-induced) immune response in people who were cured but not vaccinated for up to one year and compared it to those who had received two doses of the Pfizer vaccine (but had no previous infection. ) for 8 months. The recovered recruited – in all 130 diagnosed by molecular swab – had become infected with the original virus, with the Alpha variant of Sars-CoV-2, and in a few cases with Beta, since enrollment was completed before the advent of Delta. None of them got reinfected during the study period.
The anti-Spike IgG proteins and neutralizing antibodies of these former patients were compared with those of 402 people of corresponding age and body mass index, but vaccinated with two doses and never infected with the virus. These dual vaccinated patients also did not become infected during the study period. However, in Israel, cases of vaccinated and never infected health workers who were experiencing breakthrough infections began to emerge in the second quarter of 2021 about 6 months after the last vaccine dose. All while previously infected and unvaccinated people resisted the infection. The study aimed to understand why this difference.
The quality of antibody performance measured with the ‘avidity index’ was compared at 1 and 6 months for sub-cohorts consisting of 16 cured and 22 never infected and vaccinated people with two doses. For the healed, questionnaires were also collected on the symptoms experienced, including the Long Covid. The researchers found that the number of antibodies present in the vaccinated one month after the last dose was higher than the cured patients had. However, these numbers then declined more dramatically in the vaccinated. Initially, the greed index was higher in the vaccinated than in the recovered. But, if up to 6 months this value did not change significantly in the vaccinated, in the recovered it gradually increased and “potentially protected them from reinfection”, the experts speculate.
Then there is an ‘oversize’ effect: the level of antibodies in those healed with a body mass index of 30 or more (obese) was higher at all times than in those with a Bmi below 30 (weight from normal to overweight), suggesting that “people with obesity with a previous Covid infection were better protected against future infections”. The authors conclude that, “while the number of antibodies decreases with time in both cured (never vaccinated) and vaccinated (never infected), the quality of the antibodies increases after infection, but not after vaccination. And people with obesity have a significantly higher and sustained antibody-induced immune response after infection. ”
These results “provide specific characteristics of the immune response that may explain the differential protection against Covid in previously infected people versus vaccinated people alone.” The team of scientists is now following a group of people recovered from the Delta variant and also a separate cohort who recovered from Omicron. And it’s looking at both humoral and innate immune responses. “With Omicron – concludes Cohen – vaccinated people are better protected from serious diseases, however the fourth dose of the vaccine, now administered to many over 60s and the immunocompromised, does not seem to be protective against infection. I think the most interesting people to follow. are now those healed from previous variants and then reinfected and healed by Omicron. Hypothetically, they should have very high antibody performance against most variants“.
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