A new study has found that a single dose of the COVID-19 vaccine boosts protection against SARS-CoV-2 variants, but only in those with previous infection
Researchers have found that people who had previous mild or asymptomatic infection have enhanced protection against the Kent and South Africa variants, after a single dose of the mRNA vaccine.
In those without prior COVID-19 infection, the immune response was less strong after a first dose.
The researchers, from Imperial College London, Queen Mary University of London and University College London, analysed blood samples for the presence and levels of immunity against the original strain of SARS-CoV-2, as well as the Kent (B.1.1.7) and South Africa (B.1.351) variants.
T Cells protection
They also focused on two types of white blood cell: B-cells, and T cells. They found that after the first dose of the vaccine, prior infection was associated with a boosted T cell, B cell and neutralizing antibody response, which could provide effective protection against SARS-CoV-2, as well as the Kent and South Africa variants.
However, it remains unclear precisely how much protection is offered by T cells.
In people without previous SARS-CoV-2 infection, a single vaccine dose resulted in lower levels of neutralizing antibodies against SARS-CoV-2 and the variants, potentially leaving them at risk to infection.
Professor Rosemary Boyton, Professor of Immunology and Respiratory Medicine at Imperial College London, who led the research, 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. This study highlights the importance of getting second doses of the vaccine rolled out to protect the population.”
“Our data show that natural infection alone may not provide sufficient immunity against the variants. Boosting with a single vaccine dose in people with prior infection probably does. As new variants continue to emerge, it is important to fast track global rollout of vaccines to reduce transmission of the virus and remove the opportunities for new variants to arise.”
Professor Danny Altmann, Professor of Immunology at Imperial, commented: “At a time of generally improving outlook in those countries with substantial vaccine rollout programmes, this study reminds us of the need to be vigilant about the threat of the variants. Most vaccinated people in the UK have received just one dose. While we know this offers remarkable protection against the original virus, our data suggest this leaves people susceptible to variants of concern.”
Professor Áine McKnight, of Queen Mary University of London, said: “Our study offers reassurance and a warning. We show that current vaccines offer some protection against variants of concern. However, people who have received only the first course of a double dose vaccine show a more muted immune response. We must ensure that the global vaccination programme is fully implemented. Current events in India make painfully clear the cost of complacency.”
Professor James Moon, of University College London and Barts, said: “These results represent collaborative science at its best between hospitals, universities and public bodies providing important timely results to inform policy and strategy.”
The full study has been published in the journal Science.