What is known about the impact of the Ômicron variant on vaccine efficacy

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With the emergence of a new variant of SARS-CoV-2, the virus that causes Covid-19, the impact on the effectiveness of vaccines is one of the first questions asked by scientists.

To answer whether the immunization agents developed against Covid-19 will still be able to prevent the disease from worsening, hospitalizations and deaths, researchers are quickly mobilized to carry out studies as soon as the first cases of a new strain are confirmed.

So far, what is known is that vaccines are capable of protecting the organism from the most harmful impacts of infection with the Ômicron variant.

Studies are ongoing and are continuously providing new information on the neutralizing capacity of the immune response induced by vaccines to fight the variant.

Understand how effectiveness tests work against a new variant and the main results found so far. Manufacturers Pfizer, Coronavac and Janssen have already issued press releases about Ômicron. Oxford University and AstraZeneca did not provide information on ongoing studies.

How are tests performed?

Antibody neutralization study is one of the main methods used to assess the impact of a variant on the effectiveness of a vaccine against Covid-19.

Analyzes are performed in vitro, technical term that indicates the tests carried out in a controlled laboratory environment.

In tests, researchers verify the ability of antibodies from vaccinated people have to neutralize the Ômicron variant. To measure this impact, they use blood plasma samples from immunized individuals, where antibodies can be found, and samples of the new coronavirus or fragments of the main structures that bind the virus to human cells, such as the Spike protein.

The results identified are compared with the neutralizing capacity of antibodies against strains of the virus that circulated at the beginning of the pandemic and did not have as many mutations.

According to virologist José Eduardo Levi, from the University of São Paulo (USP), in addition to laboratory tests, clinical data can also help to clarify whether existing vaccines are losing their effectiveness against the variant.

While immunizations continue to be widely applied in the population, researchers can assess whether the vaccine response has been positive from observational studies.

Considering the places where vaccines have been made available, scientists can compare the number of infections, hospitalizations and deaths, in order to assess whether people vaccinated are among the most serious cases or among the registered deaths.

Pfizer is able to neutralize the Ômicron variant

The three-dose Pfizer vaccine is able to neutralize the micron variant of the new coronavirus. Study shows that a third dose of the immunizer increases antibody titers by 25 times compared to just two doses.

Compared to the two-dose schedule, there is a reduction in antibody titers against the Ômicron variant – but the vaccine is still able to protect against the development of serious disease.

According to Pfizer, the maintenance of protection happens because the Spike protein (used by the virus to invade human cells) can still be recognized by defense cells, even in the presence of Ômicron variant mutations.

Antibodies after the booster dose are comparable to antibody levels after two doses of vaccine against the original virus, which are associated with high levels of protection.

The information was released on December 8 by the pharmaceutical. The results are from an initial study demonstrating that vaccine-induced antibodies neutralize the Ômicron variant of SARS-CoV-2 after three doses.

Coronavac induces antibodies that recognize Ômicron

The third dose of Coronavac produces antibodies capable of recognizing the Ômicron variant, according to studies conducted in China.

The group led by scientist Xiangxi Wang, a researcher at the Laboratory of Infection and Immunity of the Institute of Biophysics of the Chinese Academy of Sciences, carried out the analysis of more than 500 units of neutralizing antibodies obtained after the application of the third dose of Coronavac.

“About a third of the antibodies showed high binding affinity to the Spike protein of the strains of concern, including Ômicron, which has more than 30 mutations,” Wang said in a statement from the Butantan Institute.

According to the researcher, the next steps include testing the ability to neutralize these antibodies against the virus, a step that will confirm their effectiveness. “I believe that at least inactivated vaccines can still work and protect against the Ômicron variant without needing an update,” Wang said.

Sinovac is already developing the Coronavac update against the Ômicron variant, which is expected to last for three months. The first step involves isolating the virus from samples from Hong Kong patients. Afterwards, tests for neutralizing antibodies will be started. The clinical trial is the final step to assess the effectiveness of the immunizer.

Janssen vaccine: ongoing studies

Janssen, a pharmacist, said the company is testing, in partnership with research groups in South Africa, serum samples from participants obtained in trials on the booster dose. Ongoing studies aim to investigate the neutralizing activity of the vaccine against the Ômicron variant.

In addition, Janssen informed that it works in the search for a specific vaccine for Ômicron, which will be developed, if necessary.

“The new Ômicron variant highlights the importance of ongoing surveillance, testing and vaccination to prevent hospitalizations and deaths from Covid-19. We remain confident in the humoral and cell-mediated immune responses produced by Johnson & Johnson’s Covid-19 vaccine, demonstrated by the durability and breadth of protection against variants to date in clinical studies,” said Mathai Mammen, global head of research and development at Janssen, in a statement.

On Dec. 5, the drugmaker released results of a study that showed that a booster dose of Janssen, when given six months after a primary two-dose regimen of Pfizer’s vaccine, increased both antibodies and the cellular immune response, which involves the activation of defense cells called T lymphocytes.

According to Janssen, the results show that the combination between the two vaccines (heterologous regimen) can bring benefits for the protection of the organism. The study results were published in an article in preprint format (no peer review).

Reference: CNN Brasil

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