According to a report, a single dose of the Covid-19 vaccine increases defence against SARS-CoV-2 coronavirus strains, but only in those that have already been infected with the disease. The researchers looked at variants in the United Kingdom and South Africa, but they believe the results could extend to other variants in circulation, such as those in Brazil and India.
The results, which were published in the journal Science, indicate that the immune response to coronavirus variants of concern may be inadequate in people who have never been infected and have only received one dose of vaccine.
Immune responses in UK healthcare staff at Barts and Royal Free hospitals after their first dose of the Pfizer/BioNTech vaccine were studied by researchers from Imperial College London, Queen Mary University of London, and University College London.
After a single dose of the mRNA vaccine, people who had previously had moderate or asymptomatic infection had substantially improved safety against the Kent and South Africa strains. After a first dose, those who had not previously received Covid-19 had a weaker immune response, possibly putting them at risk of variants.
Professor of Immunology and Respiratory Medicine at Imperial College London, Rosemary Boyton, who led the study, said. “ Our findings show that people who have had their first dose of vaccine, and who have not previously been infected with SARS-CoV-2, are not fully protected against the circulating variants of concern.”
He further added, “ This study highlights the importance of getting second doses of the vaccine rolled out to protect the population,”
The researchers looked at the blood samples to see whether there was any immunity to the original strain of SARS-CoV-2, as well as the Kent and South Africa strains that were causing concern. In addition to antibodies, the researchers concentrated on two types of white blood cells: B-cells, which remember’ the virus, and T cells, which assist B-cell memory and recognise and kill coronavirus-infected cells.
A single vaccine dose, on the other hand, resulted in lower levels of neutralising antibodies to SARS-CoV-2 and variants in people who had never been infected with SARS-CoV-2, possibly leaving them vulnerable to infection and emphasising the value of the second vaccine dose.
Based on genetic variations between people, the mutations in the Kent and South Africa variants resulted in T cell immunity that could be decreased, improved, or unchanged compared to the original strain.