Accumulating evidence suggests that the fourth dose of Covid-19 messenger RNA vaccines, which are those of Moderna and Pfizer in Spain, will be primarily important in helping people with the most vulnerable immune systems and the elderly get a better to offer protection. However, the studies published in December show that a fourth dose is unable to enhance or prolong the immune response already triggered by the third dose.
It is possible that there are vaccination schemes with recombinant proteins that can enhance this reaction. We have to confirm this with ongoing clinical studies, since almost all studies to date have been carried out with messenger RNA vaccines. An example of a recombinant protein vaccine is the Spanish one from Hipra, which is currently in a clinical trial and is expected to be approved in the coming months.
Currently, when we talk about messenger RNA vaccines, we know that the third dose strengthens the immune response for longer compared to the second dose. However, the fourth dose does not exceed the maximum levels achieved with the third, and its effects wear off about three months after vaccination. Therefore, the timing of vaccination should coincide with situations where community transmission is high and the risk of contagion is very high. With that in mind, the next booster doses of the vaccine should be scheduled to fall during higher-risk times of the year, as is the case with the flu shot.
But let’s not forget that the fourth dose has value for vulnerable populations. Compared to the third, the fourth doses of mRNA vaccines given during the period when the Omicron variant was predominant reduced the risk of death in people living in institutions and in the elderly for at least two months. These results suggest that a fourth dose can prevent mortality in vulnerable populations, but they also show that the protective effect is temporary, which will force us to look for the epidemiological moments of greatest risk to anticipate the am vaccinate those most at risk.
Anticipation and ability to provide booster doses of the Covid vaccine to vulnerable populations who are elderly or immune-compromised will be key to curbing the excess mortality we have continued To in 2022 in countries with comprehensive immunization coverage. like Spain.
We have to keep in mind that after being infected with the virus, our immune system responds optimally to a new infection for a few months, and we must therefore take these episodes into account when deciding whether to re-vaccinate. It would not make sense to receive a booster vaccination immediately after an episode of infection .
Nuria Izquierdo-UserosShe has a PhD in Biology and is the leader of the Emerging Pathogens group at IrsiCaixa.
Question by email from Julio Alonso
Coordination and writing:Victoria Bull
we answeris a weekly scientific advisory session hosted by the Dr. Antoni Esteve Foundation and the L’Oréal-Unesco program “For Women in Science” and answers readers’ questions about science and technology. They are scientists and technologists, members of AMIT (Association of Women Researchers and Technologists) who answer these questions. Send your questions to [email protected] or on Twitter #weanswer.
The advice given by this office is of a general nature and does not replace medical advice. If you have any questions about your specific problem, ask your doctor or pharmacist.
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