A single dose of vaccine boosts protection against SARS-CoV-2 coronavirus
variants, but only in those with previous COVID-19, a study has found.
In those 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.
The findings, published today in the journal Science and led by researchers
at Imperial College London, Queen Mary University of London and University
College London, looked at immune responses in UK healthcare workers at Barts
and Royal Free hospitals following their first dose of the Pfizer/BioNTech
vaccine.
They found that people who had previously had mild or asymptomatic infection
had significantly enhanced protection against the Kent and South Africa
variants, after a single dose of the mRNA vaccine. In those without prior
COVID-19, the immune response was less strong after a first dose,
potentially leaving them at risk from variants.
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.”
Blood samples were analysed 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 of concern. Along with antibodies – the Y-shaped
proteins which stick to the virus and help block or neutralize the threat –
the researchers also focused on two types of white blood cell: 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 neutralizing antibody response,
which could provide effective protection against SARS-CoV-2, as well as the
Kent and South Africa variants.
However, 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 vulnerable to infection and
highlighting the importance of the second vaccine dose.
The team looked at two variants of concern, however, they think it possible
that the findings will apply to other variants in circulation, such as the
Brazil (P.1) and India (B.1.617 and B.1.618) variants.
It remains unclear precisely how much protection is offered by T cells.
Interestingly, the mutations in the Kent and South Africa variants here
resulted in T cell immunity which could be reduced, enhanced or unchanged
compared to the original strain, depending on genetic differences between
people.
Professor Boyton commented: “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.”
Reference:
Reynolds CJ, Pade C, Gibbons JM, et al. Prior SARS-CoV-2 infection rescues B
and T cell responses to variants after first vaccine dose. Science.
Published online April 30, 2021:eabh1282. doi:
10.1126/science.abh1282