Read here, what causes Coronavirus infection, even after a full vaccination?

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• Apr 28, 2022 | Poonam Nath

People who are fully vaccinated and boosted produce antibodies that can fight the original strain of SARS-CoV-2

Digital Desk: One possible explanation why, after two vaccination doses and a booster shot, you were still sick from the Omicron strain of Covid-19, the possible answer may be that it could be the antibodies fighting the original virus are weaker against the extremely infectious variant.

While people who have been fully vaccinated and boosted produce a high level of antibodies that work against the original strain of SARS-CoV-2, the same tiny guards do not work as well to prevent the Omicron strain from attacking healthy cells to researchers at Johns Hopkins University in the United States.

Joel Blankson, Professor of medicine at the varsity's School of Medicine, explained: "Previous research has shown vaccine-induced antibodies respond to the original strain of SARS-CoV-2 by inhibiting the virus's ability to bind to angiotensin-converting enzyme 2 [commonly known as ACE2], the receptor on a cell's surface through which SARS-CoV-2 gains entry."

"According to the results of our study, these antibodies inhibit ACE2 less efficiently with the Omicron strain, opening the door to a breakthrough Covid-19 infection," he said.

Blankson and colleagues examined both humoral (SARS-CoV-2) specific antibodies circulating in the bloodstream and produced by B lymphocytes or B cells) and cellular (direct attack on the virus by T lymphocytes, or T cells) immune responses in 18 healthy and fully vaccinated people who experienced groundbreaking infections from 14 to 92 days after receiving a Covid vaccine booster.

The humoral and cellular immune responses of those with breakthrough infections were compared to those of a control group of 31 participants, ages 21 to 60, who also received Covid vaccinations and boosters and had no prior SARS-CoV-2 infection.

Blankson explained, "When we tested antibody-mediated inhibition of SARS-CoV-2 spike protein binding to ACE2, we discovered that serum from study participants with breakthrough Covid-19 - most likely the result of Omicron infection - had antibodies that strongly stopped binding by the original strain virus as expected but did not carry out that function as well when responding to the Omicron strain."

The antibodies that inhibited spike protein binding to ACE2 - high for the original strain virus but lower for Omicron - were comparable in both the participants with breakthrough infections and the control group.

"The comparable strong T cell responses for the original and Omicron strains may explain why people with breakthrough Covid-19 cases typically experience only mild symptoms during their illness," Blankson said.

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