A single dose of the vaccine increases protection against variants of the SARS-CoV-2 coronavirus, but only in those who have previously had Covid-19.
According to a study published in “Science”, the immune response to the variants may be insufficient in those who have not been previously infected and have only received one dose of vaccine
The study, conducted by researchers from Imperial College, Queen Mary University and University College, all of them in London, analyzed the immune responses in healthcare workers at three UK hospitals who had received their first dose of Pfizer/BioNTech.
In this way, they saw that those who had previously had a mild or asymptomatic infection had better protection against the SARS-Cov-2 variants of Kent and South Africa, even though they had only received a single dose of the mRNA vaccine.
However, those who had not had previous Covid-19, had a less strong immune response, which made them more sensitive to the new variants.
“Our findings show that people who have received their first dose of vaccine and who have not previously been infected with SARS-CoV-2, are not fully protected against circulating variants. This study highlights the importance of full vaccination, with the second dose, to achieve complete protection, ”says Rosemary Boyton, Imperial College London, who led the research.
The study is very comprehensive because it has analyzed blood samples to determine the presence and levels of immunity against the parent strain of SARS-CoV-2, but also against the Kent (B.1.1.7) and South Africa (B .1.351).
In addition to antibodies, the Y-shaped proteins that stick to the virus and help block or neutralize the threat, the researchers also focused on two types of white blood cells: B cells, which are reminiscent of the virus, and T cells, which help to the memory of B cells and recognize and destroy cells infected with coronavirus.
Thus they discovered that, after a first dose of vaccine, previous infection was associated with a response of T cells, B cells and neutralizing antibodies, which could provide effective protection against SARS-CoV-2, as well as the Kent and South African variants.
However, in people who had not had Covid-19, a single dose of the vaccine generated lower levels of neutralizing antibodies against it. SARS-CoV-2 and variants, which leaves them potentially vulnerable to infection and highlights the importance of the second dose of vaccine.
The team only looked at these two variants but they believe the findings may be applicable to other variants, such as Brazil (P.1) and India (B.1.617 and B.1.618).
Professor Boyton commented: ‘Our data show that natural infection alone may not provide sufficient immunity against variants,’ he notes. Boyton. And he adds that single-dose booster in people is likely to “do.”
For Imperial College professor Danny Altmann, the study reminds us of the need to be aware of the threat of variants because there are many people who have only received one dose.
«Our study offers reassurance but also a warning. We have shown that current vaccines offer some protection against some variants. However, people who have received only the first round of a vaccine show a weaker immune response. We must ensure that the global vaccination program is implemented, ”concludes Áine McKnight of Queen Mary University of London.