Leading immunologists have questioned the strategy of administering third doses to the entire adult population. They argue that even if antibody levels decline after 4, 5, or 6 months, cellular immunity constitutes a defensive ‘army’ capable of staving off severe disease and death. They support booster vaccination of vulnerable people, older people, who take immunosuppressive drugs or are immunocompromised, since the third administration confers immunity similar to that of the rest of the population with two doses. However, they warn that it is not clear that it is necessary for the general population and indiscriminately, especially in young people who do not suffer from serious illness. In addition, they recall that the high percentage of those infected by the omicron variant – which the WHO estimates at 50% of Europeans within two months – who are already vaccinated will have powerful hybrid immunity (two doses plus infection).
This is the position of well-known immunologists such as Africa González, professor at UVigo, and Alfredo Corell, professor at the University of Valladolid, who has criticized the fact that the Conference on Vaccines does not include any immunologist.
The European Medicines Agency (EMA) itself expressed its doubts on Wednesday about the need to “continually” administer booster doses of the covid-19 vaccine. The EMA agrees with Africa González, who warned a long time ago that “repeated administration can produce the opposite effects to those expected, with a lesser response.” As he explained, very repeated doses can induce an effect called “tolerance”, which is what is intended with allergy vaccines.
Another prominent scientific voice that has questioned this strategy has been that of Eduardo López-Collazo, scientific director of the Research Institute of the La Paz University Hospital, in Madrid. López Collazo has defended that to administer a third dose, it would be necessary to know what the cellular immunity of each person is and thus be able to implement a personalized vaccination schedule. However, it is much more complex to measure cellular immunity than humoral immunity –antibody immunity–, which is evaluated by means of a simple and cheap serological test, something that does not yet exist for cellular response.