Booster dose may increase risk of reinfection with Covid, new study concludes

The booster dose or third dose in some cases can leave those inoculated more vulnerable to reinfection with Covid than better protected, reveals a new study from Qatar, published on the 1st in a database of articles awaiting analysis from specialized journals (so-called pre-press articles or “preprints”). Two doses can help prevent reinfection, but the third dose doubles the risk.

Scientists observed that the group of participants who had taken three doses and had already recovered from the infection with the variant omicron had more reinfected than the group of those who only took two doses.

The authors’ explanation for the results is a phenomenon called original antigenic sin. When the body encounters a pathogen such as a virus, it develops defenses in the form of antibodies and memory cells. When there is a reinfection, this memory is activated and antibodies are produced again. However, if the virus that is returning is slightly different from the one referring to the stored memory, as is the case with variants, the defenses triggered may be ineffective, and the virus does more damage. So there is an “original sin”: what was originally done by the immune system is a “mistake” when applied to the new infection. The effect is also known as “imprinting immunological”.

However, the scientists involved in the study think that their findings do not undermine the potential benefits of the third dose, at least in the short term, for the public. “There is no question that the booster shot reduced the incidence of infections soon after it was administered,” they say, but “the findings indicate that the short-term effects of the booster shots may differ from their long-term effects.”

The effect was predicted

None of the reinfections observed in the study were severe, as is the general case now that Covid-19 is primarily caused by viruses of the ômicron variant and its subvariants.

Hiam Chemaitelly, from Cornell University in Doha, Qatar, is the first author of the study, led by Laith J. Abu-Raddad, from the same institution, who also works at the World Health Organization. Abu-Raddad and his team in Qatar have been the source of some of the best studies on infection, reinfection and natural immunity in the pandemic.

A publication by Adam K. Wheatley of the University of Melbourne, Australia, had already predicted the effect in September 2021. “We hypothesized,” Wheatley and his collaborators said in the paper, that Covid vaccines 20 made based on the new variants “may be ineffective due to imprinting immunological vaccination or previous infection.”

For Daniel Altmann, professor of immunology at Imperial College London, antigenic original sin happens in some people due to the various ways in which they were immunized, from previous infection with different variants to different vaccines such as Coronavac, AstraZeneca, Janssen and Pfizer. “All these things pull and push your immune repertoire and antibodies in different directions, and make you respond differently to the next vaccine that comes along,” Altmann told Medical News Today. . These different stimuli in different people lead to different responses of their bodies, which include imprinting.

Bivalent Reinforcement

Two months ago, based only on a preliminary rodent study, the US Food and Drug Administration (FDA) authorized another booster dose that targets two subvariants of the omicron, BA.4 and BA.5. It is the so-called bivalent vaccine, produced in two versions by pharmaceutical companies Pfizer and Moderna. More than 20 millions of Americans have taken the bivalent booster dose. Prestigious universities in the country raised controversy by reintroducing “vaccination passport” that requires this dose of students, professors and staff to return to school, which is a form of coercion.

In a note, BioNTech, which is a partner of Pfizer in the production of the vaccine, disclosed that this dose increased by four times the amount of antibodies against the two subvariants in laboratory tests, compared to the original vaccine. But the result is valid only for individuals aged 2021 years or older.

Vinay Prasad, professor of epidemiology and biostatistics at University of California, San Francisco, was surprised by the lack of information from the manufacturer regarding the effects on patients between 20 and

years and the way the note was covered by the press. He explains that the increase in the antibody response does not necessarily translate into more immunization.

In his own publication, Prasad complained that the experts interviewed are people with a conflict of interest, as they receive money from the Pfizer. “We don’t want political leaders playing doctor,” he commented on the White House’s direct involvement in promoting bivalent dosing after meetings with drugmakers. “Make the manufacturer that is earning tens of billions of dollars carry out the proper study before launching [a vacina] on the market”, concluded the expert.


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