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The first two vaccinations approved in the West against SARS-CoV-2 coronavirus, the BNT162b2 of Pfizer-BioNTech andMRNA-1273 of Modern Inc. and National Institute of Allergy and Infectious Diseases (NIAID), both should be administered with a double dose, as is the case with many other vaccines (for example, measles). The reason lies in the fact that if the first dose, technically called “priming“- it is necessary to develop the immune response, the second – or increase – It is essential to enhance it and make it more effective in preventing the disease. In other words, after the first injection, the neutralizing antibodies againstantigens – in the specific case the protein S OR Spike coronavirus, but it is only with the second that they are produced in sufficient quantities to guarantee high protection, thanks to the generation of so-called “memory cells BThey have the function of remembering the invader and producing an army of antibodies / immunoglobulins when necessary. According to a new study published in Science Immunology, COVID-19 (the infection caused by the coronavirus) determines an immunity that lasts at least eight months, which is why it is believed that that of vaccines is at least as long, although will confirm with inquiries. ad hoc.
For both the Pfizer-BioNTech and Moderna-NIAID preparation, both vaccines based onMessenger RNA (MRNA), the administration of the second dose is scheduled at 3-4 weeks from the first, so there is a fairly wide window of time during which only the first is covered. Based on charts published by the Food and Drug Administration (FDA) American, the agency responsible for the regulation of food products, experimental therapies and medicines, until about the tenth day, the infection curve overlaps both in patients treated with placebo than in those treated with the vaccine, and then they began to diverge and skyrocket dramatically only in the placebo group. This means that even after a single injection there is a high degree of protection against SARS-CoV-2, which, however, is still not sufficient. In the case of the Pfizer and BioNTech vaccine, for example, as reported in the approval document published by the FDA, the efficacy of a single dose in 21 days is 82 percent, while 14 days after the second dose is approximately 95 percent. Beyond the 21st there is not enough data. Also in the document dedicated to the approval of the Moderna-NIAID vaccine it is specified that “there appears to be some protection against COVID-19 after a dose”, however, adds the FDA, the data is not sufficient to have information “on the long-term protection beyond 28 days after a single dose. “
Ultimately, with a single dose you get some protection, but it is not comparable to that of the two doses, so there is certainly a greater risk of contracting the infection than with double administration. Think that, by analyzing the data related to severe cases After a single injection of Moderna or placebo vaccine, the FDA detected two severe cases in the vaccine-treated group and four in the placebo group. However, with the double dose, one determines full protection against the severe form of infection. Regarding the vaccine AZD1222 developed in collaboration between scientists at the Jenner Institute ofOxford University, from the Italian biotechnology company Advent-Irbm (Pomezia) and the pharmaceutical company AstraZeneca, a note was issued specifying that “after at least 21 days from the administration of the first dose there were no serious cases”, while ten patients from the control group were hospitalized, two of them developed the severe form of COVID -19 and one lost his life. In this case, the single dose would appear to have been more effective in preventive terms.
Therefore, in light of these results, it can be concluded that it is possible to contract thesymptomatic infection between the first and second doses of the vaccine, and that in some cases even the serious one can be determined, since the protection is not comparable to that offered by the standard double dose. Therefore, the recommendation is to stick to the standard two-dose administration when it is your turn. The vaccination campaign is about to start now also in Italy (and in the rest of Europe); Starting on December 27, the first injections will be carried out at the Lazzaro Spallanzani institute in Rome, while all Italians are expected to be vaccinated by the summer-fall of 2021.
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