The antibodies produced as a result of infection by one variant of SARS-CoV-2, the virus causing COVID-19, are able to bind to and stop other variants from entering the host cells in order to replicate, researchers have found.

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Understanding how some variants may be able to trigger an effective antibody response against other variants, in addition to itself, could help inform future vaccine design, said the team from Francis Crick Institute and University College London Hospitals NHS Foundation Trust (UCLH).

In their study, published in the journal eLife, the scientists analysed blood samples collected from patients who had previously been infected with COVID-19 and who were admitted to UCLH for other reasons, samples from health care workers as well as samples collected from patients at different points earlier in the pandemic.

They identified COVID-19 antibodies in the blood, and in the lab ran tests to see if antibodies produced after infection with one variant were able to bind to and neutralise other variants. The study included: the original strain first discovered in Wuhan, China; the dominant strain in Europe during the first wave in April 2020 (D614G); Alpha (B117), first discovered in the UK; and Beta (B1351), first discovered in South Africa.

The researchers found that antibodies produced by the Alpha variant were not able to neutralise the original or D614G strains as effectively, in comparison to neutralising the Alpha variant itself. Antibodies produced against infection with the D614G strain were able to neutralise both the Alpha and original strains to a similar level as D614G.

Both the Alpha and D614G strains produced antibodies which were not able to effectively neutralise the Beta strain. There are many elements of the immune system which impact how protected an individual may be against future disease. This includes memory B cells and T cells which equip the immune system to deal with evolving threats. As a result, these findings do not necessarily mean people who were infected with specific variants are less protected against others.

"It's important to note that most people who have been infected with the virus will not know which variant they were infected with and it is critical that everyone eligible for the vaccine takes up the opportunity because we know they are effective in some way against all known variants," said Kevin Ng, doctoral student in the Retroviral Immunology Laboratory at the Crick.