May 14, 2022 4:43 pm

Goodbye herd immunity?




The rapid development of vaccines against Covid led to overly optimistic initial estimates of achieving so-called herd immunity. It would be enough to vaccinate 70% of the population to drastically reduce the circulation of the virus. The reality has been different, first because the vaccines in use among us (mRNA or viral vector) do not prevent those vaccinated from becoming infected and contagious, although they drastically reduce the risk of serious illness. Second, because the successive variants become resistant to the antibodies that have been generated by infection or immunization with the original virus that emerged in Wuhan.

The Omicron variant, much more transmissible but less virulent, has broken all the schemes, and has even questioned the idea of ​​continuously vaccinating with booster doses, when it is obvious that the protection by antibodies declines a lot against it.

The call of immunological experts to examine the other arm of immunity that protects us, cellular immunity, is very reasonable; in the T lymphocytes of the immune memory is the key to a better vaccine protection against the variants.

In this situation, it is not clear that we can soon go from a Covid epidemic to a Covid endemic (the neologism “influenza” is intended to be implemented), much less that our public health measures should focus on promoting this option. The evolutionary scenario, as revealed by the magazine ‘Nature’, is far from determined. The appearance of new variants, which could be more virulent, is possible, it is conditioned first by the evolution of the virus that continues (do not forget that it also circulates in some animals such as the mink) with great opportunities for new changes due to mutation and recombination. In addition, the immune status of the world population may favor the selection of these new variant viruses, as was the case with previous ones. Updating the vaccines now is imperative, it makes no sense to vaccinate again and again against the Wuhan virus that has changed so much. Avoiding the indiscriminate spread of contagion continues to be equally necessary.

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