Omicron vaccine should contain BA.2 antigen

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Biontech scientists have discovered a potentially optimal composition of new corona vaccines against the Omicron variant that should also protect against BA.4 and BA.5 subtypes.

A covid-19 vaccine that is more effective against SARS-CoV-2/Omikron should ideally contain – in addition to the antigens used initially (wild-type/Wuhan) – an antigen of the omikron subtype BA.2. This is because it can also protect BA.4 and BA.5 subtypes of the Covid-19 pathogens.

Scientists tested extensively for the virus neutralization potential of plasma samples (antibodies) after vaccination and breakthrough infections. A key finding, as reported online Wednesday by the German Pharmaceutical Newspaper, was that “those who are primed with the mRNA-based corona vaccine ‘Comirnaty’ (BioNTech/Pfizer) and subsequently contract an omicron BA.1 breakthrough infection develop strong serum neutralization activity against omicron BA.1 and BA.2 variants, as well as against earlier SARS-CoV-2 variants of concern (VOC). However, against the highly contagious omicron sublines BA.2.12.1, BA.4, and BA.5, omicron BA.1 breakthrough infection is hardly protective.”

This is understandable, he said, because BA.2.12.1, BA.4, and BA.5 have little proximity to BA.1 in terms of their proteins (antigens). The three virus variants originated from BA.2 viruses by mutation. This suggests that patients who have undergone a BA.2 breakthrough infection also build up some protection against the omicron variants BA.2.12.1 and BA.4/BA.5. The scientists tested this hypothesis, which eventually proved correct.

Antibody after BA.2 infection provides better cross-reactivity.
The better cross-reactivity after infection with BA.2 is apparently that the affected individuals form antibodies against one end of the spike protein (N-terminal domain), which has a similar structure in BA2, BA.4, and BA.5, i.e., it is “conserved.” BA.1 breakthrough infection after vaccination, on the other hand, results mainly in antibodies against the receptor-binding parts of the spike protein. But these differ significantly between BA.1, BA.4, and BA.5, resulting in little cross-immunity.

“These results are of great importance for the development of vaccines adapted to Omicron and suggest that an adapted vaccine may be better to contain a BA.2 than a BA.1 component,” the German pharmacy journal said. The adapted. Covid-19 vaccines likely to hit the market in the coming months will all likely contain at least two antigenic components: one against the original wild-type SARS-CoV-2 and one that protects against currently circulating variants.

Only “narrow” protection after omicron infection
Just a few days ago, scientists at MedUni Vienna’s Center for Virology showed in Frontiers of Immunology that infection with BA.1 or BA.2 alone produces only a very “narrow” immune response against the virus subtype responsible for the disease in each case. In the end, these research findings also supported the plan to include both SARS-CoV-2 wild-type antigens and those from Omicron in future vaccines. According to the BioNTech scientists, antigens of the BA.2 subtype appear to be the most likely.