The declaration of the World Health Organization (WHO) on the need to develop anti Covid vaccines with a high impact on the prevention of transmission, as well as of the disease, responds to an appeal that the scientific community has been making for months.
"It is an appeal that the scientific community has been making for months", commented virologist Francesco Broccolo, of the University of Milan Bicocca.
According to the expert, the European Medicines Agency (EMA) also stated on the lack of data to support an additional booster dose goes in the same direction.
"We are finding that chasing after the virus is not a winning solution. Under selective pressure, in fact, the virus continues to mutate, while we are continuing to use the booster of a vaccine designed to respond to the Spike protein of the original SarsCoV2 virus. Consequently - the virologist noted - in order to have coverage of the disease, increasingly close calls are now required and the duration of protection for which is not actually known ".
On the hypothesis of a fourth dose at a distance of 4 or 5 months, Broccolo observed that "in the history of vaccination we have never gone beyond three doses" and that "it is not by raising the antibody titre that protection is achieved, if the antibodies are not are specific against the variant in circulation ". Continuing on this path means continuing in a "strategy that runs after the virus".
On the other hand, following a new strategy means "using vaccines updated on the latest variants and, above all, that also take into account other targets that modulate protection";
it also means having "vaccines capable of blocking infection, such as spray vaccines".
These are ideal, considering that "the virus enters the nasal mucosa where many receptors of the SarsCoV2 virus are expressed. Consequently, intervening with the vaccine on the mucous membranes means blocking the main gateway of the virus".
The current vaccines are instead injected intramuscularly and produce antibodies in the blood, but the virus in the blood is little, even in sick patients ".
