• Mon. Oct 25th, 2021

Covid vaccine, third dose hypothesis: “very likely” for experts

Byeditorial

May 5, 2021

The hypothesis of a third dose of the anti-Covid vaccine to be administered in November to health professionals and over 80, the first to have vaccinated, is growing. After Pfizer / BioNTech talked about a probable booster 6-12 months after the second dose – and an annual booster thereafter – scientists and experts agree to recommend further inoculation, although for some it is a decision. which must be taken on the basis of clinical data. PREGLIASCO “A further recall of the anti-Covid vaccine”, with the third dose “was already planned. The data are still to be confirmed with respect to the duration of protection, in addition we see that the disease after six months in some cases determines already reinfection and therefore there may be this need in subjects most at risk and in subjects most exposed “, virologist Fabrizio Pregliasco, professor at the University of Milan, tells Adnkronos Health. “I believe that there is also the possibility – underlines Pregliasco – of an updated vaccine. We will have to see the authorization times for this vaccine, because as happens with the flu there is a verification, albeit more limited”. MASTROIANNI “The third dose” of the anti-Covid vaccine “at the end of the year for healthcare workers and the elderly, I think it will be very likely. However, the ongoing studies will also be analyzed, the viral variants in circulation evaluated, the antibody titer verified at 5 -6 months after the second dose and what kind of epidemiological situation we will have in November-December “. Claudio Mastroianni, director of the Infectious Diseases Department of the Policlinico Umberto I in Rome, says this to Adnkronos Health. “We must remember that V-Day in Italy was at the end of December 2020: the first doctors and nurses will almost certainly have to do a recall one year after the vaccine”, suggests the infectious disease specialist. BASSETTI “I would be cautious about the possibility of doing a third dose of the anti-Covid vaccine. We do not have certain data on when to do it from the first: 6 months or 12 months? It would be better to wait for certain data on the duration of immunity and then understand how to move. doctors and health workers would mean doing a third dose in late November and December. ” So to Adnkronos Salute Matteo Bassetti, director of the Infectious Diseases Clinic of the San Martino hospital in Genoa and member of the Covid-19 crisis unit of Liguria. GISMONDO There is no basis for being able to express oneself according to evidence according to Maria Rita Gismondo, microbiologist at the Sacco hospital in Milan. “At this moment it has no scientific basis, neither to say that a third dose of the anti-Covid vaccine should be done, nor to say that it should not be done”. “The recall – underlines the expert at Adnkronos Health – is made when one has the scientific certainty that the antibodies stimulated by the injection-shield have dropped. “We do not yet have data on acquired immunity, nor data on the length of time it is maintained,” notes the director of the Sacco Laboratory of Clinical Microbiology, Virology and Diagnostics of Bioemergencies. A possible recall “we will be able to decide later, when 7-8 months or maybe even more have passed” from the first vaccination cycle, estimates Gismondo. ANDREONI The need to have a third dose of the anti-Covid vaccine “is almost certain. We just need to understand if it will be done within 12 months of the first. I remember that doctors and health professionals started vaccinating them at the end of December 2020. The projections of the duration of immunization tell us that it should last up to 12 months, we should have more confirmation to plan this third dose which risks complicating the vaccination campaign “, highlights to Adnkronos Health Massimo Andreoni, scientific director of the Italian Society of infectious and tropical diseases (Simit) and head of Infectious Diseases at the Tor Vergata Polyclinic in Rome. MENICHETTI, “A third dose of vaccine” against Covid-19 “could be a hypothesis if two conditions are met: a sensational drop in the level of protective neutralizing antibodies induced by the vaccine, documented by serological tests, or the preponderant emergence of poorly responsive variants to the vaccine like the Brazilian, the South African and the much feared Indian variant “, comments the virologist Francesco Menichetti, head of infectious diseases at the Pisa hospital. “For me – he underlines – it would make more sense to work on an updated booster dose, because if one has to redo the same vaccines that are available now, I have some doubts. Instead, the possibility of having updated versions of the vaccines soon available. , especially those with messenger Rna which are the most flexible and most rapidly modifiable, would be better “.
A recall with the old vaccine, Menichetti specifies, “must be a choice substantiated by a serious check of antibody levels. Because – explains the virologist – is it plausible that in the over 80s the response to the vaccine is modest and of limited duration due to age that attenuates the extent of the immunological response, in healthcare personnel who on average have a lower age there should be no major problems, considering that these vaccines not only induce neutralizing antibodies, but also create the immunological memory which is that carried out by the cellular immunity that when it re-encounters the virus remembers and takes the field. So – he concludes – rather than open a debate, let’s organize ourselves to check the levels of immune protection on a significant sample “. MAGA (CNR) “The recall of a vaccine always makes sense if there is evidence that immunity can weaken. If, now, with the accumulation of data coming from the vaccination campaign, a possible risk of lowering immunity or if any viral strain particularly resilient to vaccination were to be presented, the recall could be justified. But it all depends on the data “, virologist Giovanni Maga, director of the Institute of Molecular Genetics of the Cnr of Pavia, explained to Adnkronos Salute. “It is a decision – reiterates Maga – that must be taken on the basis of clinical data, not without a premise. For the moment there are no data that seem to indicate the need for a recall, but it is a possibility. a recommendation to follow if given “.