but how long does vaccine protection last? – time.news

from Laura Cuppini

We are discussing an extension of the green pass, bringing its validity from 9 to 12 months. The variation to the study of the Ministry of Health. Abrignani: Before thinking about a possible third dose, it is necessary to reach 80% of the vaccinated population

The green passes of the first vaccinated (in January) expire in October, because the duration of 9 months from the date of the second dose. For the healed instead the green pass lasts 6 months from the negative molecular buffer e 9 months from administration of the single dose of vaccine, scheduled between 3 and 6 months after healing.

Green pass a 12 mesi

To solve the problem of the expiry of the certificate, the most popular hypothesis at the moment, as explained by Franco Locatelli on Courier service
, the one of extend the green pass to 12 months for all vaccinated
(with two doses and cured with one dose). To date, 68% of the population over 12 vaccinated with two injections (here the report updated in real time), therefore misses the appeal, or must complete the cycle with the second injection, the 32% (just over 19 million people). For the moment there have been no government decisions regarding the third dose. The hypothesis of extending the green pass to 12 months is more than reasonable, also in light of the progressive acquisition of information on the duration of the vaccination response – explains Locatelli -. The deadline was initially set at 6 months, and then stopped at 9, precisely because how long the protective effect conferred by the vaccine lasts we are gradually learning. The first vaccinations in the world started about 10 months ago. As there is currently no evidence that there is a substantial loss of the protective effect offered by immunization in the first vaccinated, the choice of extending the expiration to 12 months has a solid basis.

The hypothesis of a third dose

The third dose, for which scientific evidence demonstrates a stimulating effect (effect booster) on “memory” lymphocytes, of course necessary as soon as possible for the immunosuppressed – adds Locatelli -. The vaccination campaign still in progress has been completed, it will be possible, on the basis of the evidence on the duration of the protection conferred by vaccination that will become available, to evaluate if and when to give the third dose also to people with particular frailties or very exposed to the risk of infection for professional reasons.

The duration of immunity

One of the central points of the question is the duration of immunity offered by vaccines. We do not know fully to answer, given that the follow-up of vaccinated people is still too short – he says Gianni Rezza, general director of Prevention at the Ministry of Health, in an intervention published also in the Courier service
-. It seems that even though neutralizing antibodies tend to drop over time, cellular responses and memory of encountering the viral antigen persist. longer than previously thought. Compared to Delta variant (Indian), vaccines remain highly effective in protecting us from severe forms of disease, but are not always able to avoid infection (about 15-20% of vaccinated people remain uncovered, ed) – continues Rezza -. We must vaccinate as much as possible to promote a return to normal, protecting the population from the worst consequences of the disease and avoiding the congestion of health facilities.

80 percent coverage

Before starting the possible administration of the third doses, there are in fact several million people to be vaccinated with the second (or both). It will take about another month and a half to reach 80% of the vaccinated population, which is the goal – he says Sergio Abrignani, full professor of general pathology at the State University of Milan and director of the National Institute of Molecular Genetics Romeo and Enrica Invernizzi, as well as a member of the technical-scientific committee for the Covid emergency -. Therefore around the beginning of October it will be possible to concretely decide something on the third doses, which will probably be made with mRna vaccines and with those based on recombinant proteins that should arrive soon. Not said that we need specific formulations against the new variants. As for the vaccine induced protection – continues Abrignani -, we do not yet have strong data on the long-term risk of serious illness, while we know that the likelihood of contagion (with mild or no symptoms) increases already 3-6 months after vaccination. In this moment, it is necessary to give oneself priorities and the fundamental thing is to reach 80% coverage with the first two doses.

The various aspects of immunity

Fabrizio Pregliasco, professor at the University of Milan and health director of the Galeazzi Orthopedic Institute, underlines: To date there is no standardization of tests and there is no level of antibodies considered protective. It is being studied. Then there is not only the quantity of antibodies, there are neutralizing antibodies, there is the activation of B lymphocytes that can be measured. Some studies say that already after 5 months there is a decrease, let’s say that the duration of protection is around 9 months according to various articles still without meta-analysis. But the actual figure we will have a year after the first vaccinated and from clinical trials, otherwise a mathematical model that does not show objectivity and effectiveness in the field. Absolutely convinced of the validity of vaccines 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, who sees the green pass as a tool also for returning to school in peace: I see no other solution than the green pass, for both teachers and school staff. We are witnessing the demonstration that vaccines work and help us against Covid, just look at what is happening in Sicily, one of the regions with the lowest vaccination rate, where there is a resurgence of cases.

In favor of the third dose

In partial contrast Andrea Crisanti, director of the Department of Molecular Medicine of the University of Padua, who speaks of decisions without scientific evidence (regarding the extension of the green pass to one year). From what you see in Israel
– says Crisanti -, the protection offered by vaccines lasts around 8-9 months. Suffice it to say that healthcare workers are becoming infected in Israel. However, they are already doing the third dose and in a while we will understand if it is protective. Also in favor of the third collective dose Massimo Clementi, director of the Laboratory of Microbiology and Virology of the Vita-Salute San Raffaele University of Milan: In my opinion this extension (of the green pass, ed) as a simple bureaucratic step, without doing tests to understand the level of antibodies, but only if the 12 months are the prelude to a third dose, which is really important. In my opinion this should be the goal. For Silvio Garattini, president of the Irccs Mario Negri Pharmacological Research Institute, the extension of the green pass must be based on scientific grounds: it is important that it has a scientific basis, because it is useless to pretend to be protected if you do not. Also because we cannot rely on antibodies alone, we must also look at the other aspects of immunity, which are the duration of memory and the activity of cells that act against viruses.

The English study

According to a study conducted in Great Britain, the protection given by the double dose of Pfizer and AstraZeneca begins its decline within 6 months. The researchers noted that the Pfizer vaccine 88% effective in preventing infection one month after the second dose, while after 5-6 months the protection drops to 74%. With AstraZeneca 77% protection against infection one month after the second dose; after 4-5 months it drops to 67%. The study was based on data from 1.2 million users of the Zoe Covid app, developed through a non-profit initiative, in partnership with King’s College London, and funded by the Department of Health and Welfare . The study compared self-reported infections in the vaccinated group of participants and cases in an unvaccinated control group. The authors point out that while protection appears to decline, actual individual risk may vary. A reasonable worst case scenario could see less than 50% protection for the elderly and health care workers (the first to be vaccinated in Gb, ed) by winter, warns Tim Spector, scientist in charge of the study on the Zoe Covid app. It remains to be understood whether the decline in protection involves only an increase in the risk of contagion (in asymptomatic or paucisymptomatic form) or even severe forms of the disease.

August 25, 2021 (change August 25, 2021 | 19:51)

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