Pfizer/Biontech COVID-19 Vaccine Offers Protection Against Variants, But Only If You Were Infected Earlier

According to a new study, prior COVID-19 infection boosts efficacy of Pfizer/BioNTech vaccine against variants. Read on for details.

The COVID-19 virus has mutated and today there are many variants of the virus. The deadly current second wave of the pandemic is primarily attributed to the double mutant of the virus that emerged in the Indian subcontinent. Some of the variants are highly infectious and these are also throwing up new challenges to scientists. Now that scientists have developed vaccines to fight against the novel coronavirus, one thing uppermost in people's minds is whether these will work against variants of the COVID-19 virus. A team of researchers at Imperial College London, Queen Mary University of London and University College London have found that a single dose of the Pfizer/BioNTech COVID-19 vaccine may boost immunity against the coronavirus variants, but only in people who were previously infected with the deadly virus. They also highlighted the importance of a second dose. The journal Science published this study.

Previous mild or asymptomatic infection enhances protection

In people who have not previously been infected and have so far only received one dose of vaccine, the immune response to variants of concern may be insufficient, said the team of researchers. The studylooked at immune responses in UK healthcare workers at Barts and Royal Free hospitals following their first dose of the Pfizer/BioNTech vaccine. People who had previously had mild or asymptomatic infection had significantly enhanced protection against the UK and South Africa variants, after a single dose of the mRNA vaccine.

First dose less effective against variants in people without prior infection

In those without prior Covid-19, the immune response was less strong after a first dose, potentially leaving them at risk from variants. According to researchers, the findings of this study 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. This study highlights the importance of getting second doses of the vaccine rolled out to protect the population, they say.

Prior infection boosts T and B cells, neutralises antibody response

Blood samples were analysed for the presence and levels of immunity against the original strain of SARS-CoV-2, as well as the UK (B117) and South Africa (B1351) variants of concern. Along with antibodies, the team also focused on two types of white blood cells: B-cells, which 'remember' the virus; and T cells, which help B cell memory and recognise and destroy cells infected with coronavirus. They found that after a first dose of vaccine, prior infection was associated with a boosted T cell, B cell and neutralising antibody response, which could provide effective protection against SARS-CoV-2, as well as the UK and South Africa variants. However, in people without previous SARS-CoV-2 infection, a single vaccine dose resulted in lower levels of neutralising antibodies against SARS-CoV-2 and the variants, potentially leaving them vulnerable to infection and highlighting the importance of the second vaccine dose.

(With inputs from IANS)