Cellular protection against omicron remains high with 2 doses of Covid vaccine, says study

Faced with the recent explosion of Covid cases around the world driven by the omicron variant, many people have wondered if Covid vaccines remain effective.

The scientists’ main bet was for a lasting protective response against severe cases, hospitalizations and deaths, generated by memory cells capable of controlling the organism’s infection against an invader.

Although the Ômicron generates a drop in neutralizing antibodies produced after vaccination, the immunizers have so far proved to be effective in protecting against hospitalization and deaths from Covid, especially in individuals with a complete primary vaccination schedule (two doses or a single dose, in the case of Covid-19). Janssen) or who received booster shots.

Now, recently released research proves that memory immunity, produced by defense cells, remains high against the micron, as well as against other variants.

The study, which includes American and Dutch researchers, was published last Thursday (3) in the specialized journal Science Immunology.

To assess the protective response after vaccination, the scientists analyzed the antibodies and T-type defense cells (CD4+ and CD8+, responsible for attacking pathogens and infected cells) from 400 vaccinated individuals who received two doses of Oxford/AstraZeneca, Moderna, Pfizer vaccines. or single dose of Janssen and 23 people who have had Covid in the past (so-called convalescent plasma).

As the vaccine intervals are different, blood samples were collected shortly after the second dose or single dose (in the case of Janssen) and after six months of the second dose.

Then, the scientists tested in the laboratory the blood of 15 individuals who received one of the types of immunizer to measure the ability to neutralize different strains of the virus: the ancestral form of Wuhan and the beta, delta and omicron variants.

All vaccines except Janssen showed a significant drop in specific neutralizing antibodies against the so-called RBD, or binding domain region, which in the coronavirus includes the Spike S protein six months after vaccination. Despite not having such a pronounced drop, people who received the Janssen immunizer had a lower level of antibodies compared to other immunizers.

When tested against the different strains, the serum of the vaccinated and recovered individuals showed a greater reduction in the neutralization capacity against the omicron, confirming the other studies that point to a greater vaccine escape of this variant in relation to the others.

However, all vaccines produced defense cells that recognize the virus in high amounts. More importantly, cellular protection has remained constant for all forms of the virus, including the micron.

In addition, the scientists evaluated the so-called cross-reaction, which can occur when a protective response induced against one form of the virus can also act against the others.

For this, we analyzed healthcare workers vaccinated with Janssen (15 people) or Moderna (9) who received a booster dose of Pfizer about three months after the single dose of Janssen or seven months after the two doses of Moderna.

In these individuals, before the booster, neutralization was verified for the beta and delta variants, but against the Ômicron this protection was lower. A booster with Pfizer’s immunizer, however, managed to restore this protection, in addition to providing a significant increase in neutralizing antibodies.

So far, different studies have shown how the vaccines used today do not prevent infection by Sars-CoV-2, especially against the Ômicron, which is why the so-called vaccine leaks occur. The initial protection scheme, considering two doses of AstraZeneca, Moderna or Pfizer vaccines, or a single dose of Janssen, has a reduction in the ability to neutralize the virus when it comes into contact with the body.

However, the study was able to demonstrate that protection against severe cases remains, a question that was present with current vaccines. According to the research, “specific responses of T cells against the micron were minimally affected by the mutations present in the variant.”

“T cell action confers protection against severe disease, but it has not yet been possible to determine whether this is sufficient in the absence of a potent neutralizing antibody response. Most importantly, a booster dose with BNT162b2 [Pfizer] led to a significant increase in specific neutralizing antibodies against the micron, even in those individuals who did not previously have cross-protective activity.”

“Further, the fact that the additional dose restores and increases the neutralizing capacity against the micron reinforces the immediate need for campaigns for the booster dose. In the future, updated vaccine boosters against the new variants will be necessary to implement the protective response against viruses. emerging”, completes the study.