Booster dose of mRNA vaccine for immune protection against Omicron

Health officials in South Africa report that a previously unknown variant of SARS-CoV-2 is spreading rapidly. The variant, dubbed Omicron by the World Health Organization, will soon prove more transmissible than Delta, which has previously caused the majority of COVID-19 infections.

Senior author of the Cell paper, Dr Alejandro Balazs, whose lab at the Ragon Institute studies how to create immunity against infectious diseases, said.

Balazs collaborated with a team that included the lead author of the Cell paper, Wilfredo F. Garcia-Beltran, MD, a clinical pathology resident at MGH and a clinical scientist at the Ragon Institute.

The first step is to create a harmless version of Omicron called a “pseudovirus” that can be used in the lab to evaluate the effectiveness of three COVID-19 vaccines currently available in the United States, including two doses of Pfizer and Moderna and a single dose of Johnson & Johnson vaccine.

The pseudovirus that Balazs and colleagues created mimics the behavior of Omicron, having 34 mutations in its “mutant” protein that were not found in the original SARS-Cov-2 strain first detected in Wuhan, China, in December 2019. Scientists suggest that these mutations may be partly responsible for the rapid spread of Omicron worldwide.

Next, Garcia-Beltran worked with colleagues at MGH, including Vivek Naranbhai, MD, Ph.D., fellow in hematology-oncology, to obtain blood samples from 239 fully vaccinated people. one of three COVID-19 vaccines.

Study subjects include employees in the Massachusetts General Brigham healthcare system and residents of Chelsea, Massachusetts, a community with a high rate of COVID-19 infection.

“It was important for us to have a diverse population that was represented in the study,” says Garcia-Beltran. Included in this group were 70 men and women who received a third booster dose of Pfizer or Moderna vaccine, as recommended by the Centers for Disease Control and Prevention.

Blood samples were used to measure how well each vaccine produced protective immunity in the form of antibodies against Omicron pseudovirus and Delta virus and wild type. The results were impressive.

“We found very little neutralization of the Omicron variant pseudovirus when we used samples from people who had recently received two doses of the mRNA vaccine or one dose of Johnson & Johnson,” says Balazs.

“But individuals who received three doses of the mRNA vaccine had very significant nullifications for the Omicron variant.”

It is not yet clear why the mRNA enhancer significantly improves the immune defense against Omicron. However, Garcia-Beltran said one possibility is that an additional dose would induce antibodies that bind more closely to the mutant protein, increasing their effectiveness.

In addition, the booster dose can induce antibodies that target regions of the spike protein common to all forms of SARS-CoV-2. Garcia-Beltran says both theories are correct.

A three-dose mRNA vaccine regimen ?? two traditional doses and one booster dose of the Pfizer or Moderna vaccine?? provided slightly lower levels of neutralizing antibodies against Omicron than wild-type strain COVID-19 or the Delta variant.

But the results of this study strongly support CDC’s advice that the COVID-19 booster shot is appropriate for anyone 16 years of age or older and that the mRNA vaccine is preferred.

Source: Medindia


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