As the world fibrils at the idea of a third dose of vaccine to strengthen the immune response and also protect against the dreaded Delta variant, a research just published in Lancet launches a warning: it is still early to think about a third generalized dose of vaccine against the coronavirus, it is instead a priority to immunize everyone and vaccinate only the weakest with the third dose, as in some categories of immunosuppressed, although for the latter it is not yet clear whether it is more useful to receive a third dose of the same or another vaccine.
In short, to date there is no scientific evidence for a further recall for the entire population. An international group of scientists signed the analysis, including some members of the WHO (World Health Organization) and the American FDA (Food and drug administration). According to the team of researchers, the current coverage is sufficient even in severe Covid cases and has also proved adequate to counter the Delta variant.
Vaccine effective over time
The study examines dozens of research published in international journals. What emerges is that Covid-19 vaccines continue to be extremely effective against severe disease, including those from all major viral variants. By averaging the results reported by the research, vaccination was 95% effective against severe SARS-CoV-2 disease, due to both the Delta and Alpha variants, and over 80% effective in protecting against any infection with these variants.
It works more if the disease is severe
In the presence of the different variants that we know, the effectiveness of the vaccine is greater against severe disease while it is a little less effective for fighting asymptomatic forms of coronavirus or the transmission of infection. It was also concluded that in populations with high vaccination coverage the unvaccinated minority is still the main transmission factor, as well as being themselves at the highest risk of serious disease.
Vaccinate everyone
“Taken together, the currently available studies do not provide sufficient evidence of a substantial decline in vaccine protection against severe disease, and therefore hospitalization, which is the primary goal of vaccination.” While some gain may eventually be gained from the third dose, the benefits of providing protection to all who have not yet or are not fully vaccinated will never be outweighed. “If vaccines are distributed where they would do best, they could accelerate the end of the pandemic by inhibiting the further evolution of the variants,” explains the research coordinator. Ana-Maria Henao-Restrepo, WHO.
The memory
The authors point out that although antibody levels in vaccinated individuals decline over time, this does not necessarily imply a reduction in the effectiveness of vaccines against severe disease. This may be due to the fact that protection against severe forms is mediated not only by antibody responses, which may be relatively short-lived for some vaccines, but also by memory responses and cell-mediated immunity, which are generally longer lasting. So, the experts still argue, the priority is to reach those who have not yet immunized. And, should a third dose be decided, the matter will have to be considered on a case-by-case basis.
The antibodies
“The ability of vaccines to elicit an antibody response against current variants indicates that these variants have not yet evolved to the point where they are likely to escape the vaccine-induced memory immune response. Although new variants will evolve that may escape the vaccines. current vaccines, it is very likely that they do so from strains that have already become widely prevalent. However, it must be said that in some cases, the effectiveness of some strategies to enhance immunizations, such as that of a further booster, could be greater and more lasting “. A similar strategy is used for influenza vaccines, for which each annual immunization is based on the most recent data on circulating strains, increasing the likelihood that the vaccine will remain effective even if the strain evolves further.
Safe and effective vaccines
“The vaccines currently available are safe, effective and save lives. While the idea of further reducing the number of Covid-19 cases by improving immunity in vaccinated people is tempting, any decision to do so should be evidence-based and consider the benefits and risks to individuals and society. These high-risk decisions should be based on solid evidence and international scientific discussions, “adds the other research coordinator, Dr. Soumya Swaminathan, Chief Scientist dell’Oms.
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