Home » Covid, first ISS study on Italian children: the vaccine protects much less than previously thought

Covid, first ISS study on Italian children: the vaccine protects much less than previously thought

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Covid, first ISS study on Italian children: the vaccine protects much less than previously thought

On November 19th of last year I was expressing on Salute my doubts about the real effectiveness of Pfizer-BionTech’s anti-Covid19 vaccine for pediatric use (5-11 years). I was not alone in doing this and I was certainly not against vaccinating children: it was only a critical judgment on the clinical trial of that vaccine. It was authorized by the FDA for emergency use but the technical opinion of the scientific consultants of that body was not a unanimous and convinced yes, some expressed it amidst many doubts. I believe it: as a journalist of the New York Times it is not easy to say yes to a vaccine that if authorized would have been given to millions of children around the world on the basis of a clinical trial of just over two thousand children and the consequent difficulty in obtaining a reliable estimate of the safety and efficacy of the vaccine .

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As almost always happens, after the authorization of the FDA, the vaccine has also been authorized in Europe and is currently used in tens of millions of children between the United States and Europe, including Italy. Doubts about its real effectiveness, however, remained and were markedly amplified with the advent, at the end of 2021, of the Omicron variant, with its ability to evade the neutralization of the virus by antibodies.

A full-bodied and well-conducted study

Now, June 2022, researchers from the Higher Institute of Health have just published, in the prestigious medical journal The Lancet, an excellent work on vaccination in Italian children between the ages of 5 and 11. The results of this extensive and well-conducted research, the only one to date outside the United States, show that those doubts were justified. In a nutshell, the researchers examined all the children who received the two doses of the vaccine in Italy from January 17 this year, when the first Italian child completed the vaccination cycle, to April 13, and they calculated effectiveness (more correctly what we call “effectiveness”, effectiveness, the degree of vaccine protection in the real world, outside clinical trials) compared to unvaccinated controls.

770,000 children out of a population of 3 million

These are high numbers: nearly 770,000 cases of SARS-CoV-2 infection and 664 cases of COVID requiring hospitalization, in a global population of about 3 million children. With these numbers, the estimates of effectiveness are very reliable, albeit within the limits of a retrospective experiment. The results show that the protection conferred by the vaccine against infection with or without symptoms but in any case without hospitalization is 29.4% and that against serious illness (hospitalization with or without intensive care or death) is 41.1%. . Well below the efficacy calculated in Pfizer’s phase 3 trial, above 90%, but with a very wide range of credibility (67-99%). Of particular relevance is that these protective levels are lower than those that the same vaccine has conferred on adolescents and adults, on average well above 50% for infection and much higher for disease.

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The study conducted on Omicron BA 1

It is necessary to ask ourselves what could be the reasons for this, indeed very modest, protection in children of that age group. The ISS investigation was carried out during the first three months of this year, with Omicron (BA.1) as the main variant of SARS-CoV-2, a variant that has meanwhile generated various sub-variants, now dominant in the world, and with one of which (BA4 / 5) we are already dealing with today and we will probably have more in the next autumn-winter. At the time of Pfizer’s clinical trial, the dominant variant was Delta, a more aggressive viral strain than Omicron but much less transmissible and still quite close, immunologically, to the original Wuhan strain, the one with which the Pfizer-BionTech vaccine is made.

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As has been repeatedly described in this journal, Omicron, with its numerous mutations in the Spike protein, largely escapes antibody neutralization, therefore it also infects vaccinated people, but maintains good protection in vaccinated adults against serious disease which, as we know, is above all controlled by cell-mediated immune responses (memory B and T lymphocytes, cytotoxic lymphocytes) which recognize widely different and conserved spike protein epitopes compared to those recognized by neutralizing antibodies. The research of the ISS therefore highlights what was expected in the Omicron era, that is, the low protection against infection.

Not very effective: does the reduced dose have anything to do with it?

However, the low protection against the disease, significant for a rapid drop in vaccine efficacy, remains somewhat unexpected. It can be thought that the dose of the vaccine, which in children is 10 micrograms, one third of that used in adolescents and adults, is responsible for this, a choice dictated by the need to ensure a greater level of safety of the vaccine. It can also be thought that the unvaccinated controls are not, in part, true controls because a proportion of them had been infected, then naturally immunized and turned negative again at the time of the study. It is mostly known from the researches of Alexander Dowley and collaborators in the UK that these children can mount strong and lasting antibody and cellular responses that protect them from infection for a long time. It follows that in the so-called controls there are children protected from natural infection that will not become cases, artfully reducing their number and therefore vaccination protection. Other reasons are possible and must be sought.

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Do the booster? Appropriate if not necessary

Having said that, it is nevertheless important to question the consequences that the ISS research data have on the necessary public health choices in our country. The most compelling point concerns the booster dose: that is, do a vaccination booster, a third dose, even in children. ISS data clearly suggests this is appropriate if not necessary. In fact, Pfizer has already obtained authorization in the USA demonstrating that the recall causes an increase in the antibody level, even if perhaps only transiently, and a probable increase in the degree of protection.

Wouldn’t it be useful to wait for the new vaccine?

But various problems arise. The first comes from the relative low adherence to this vaccination. In the USA, only about one third of the children got the expected two doses, we do not reach the half. Will such a close third dose be accepted? Will there be any additional side effects of the booster? How long will its effectiveness last? Above all, one wonders whether it makes sense today to vaccinate a viral strain that is now practically extinct while the one in circulation is so different and so little contrasted by this vaccine. Would it not be correct, given the low incidence of serious disease in children of this age group (see next paragraph), to wait for the formulation of a new vaccine, calibrated on the new variant? International regulatory authorities are looking into a couple of them, at least one may also be available for children in the not too distant time, perhaps as early as next fall. The first data released by Pfizer and Moderna, the two companies that tested them (in particular the bivalent of Moderna) indicate high protection against all sub-variants of Omicron, including BA.4 and BA.5.

Take into account the low incidence of severe Covid in children

As I mentioned above, it is also important to take into account the real incidence of a serious COVID in Italian children aged 5-11. In the ISS publication, in an observation period of just under three months, out of almost one million and eight hundred thousand unvaccinated children there were several hundred hospitalized children, of which fifteen required intensive care and two died, one of which suffering from a serious underlying disease. It is comforting that none of the vaccinated children, although hospitalized, needed intensive care or died. However, this is a very small risk of serious disease (around 2 in a hundred thousand for intensive care and less than 1 in a hundred thousand infections for death) which cannot fail to generate great uncertainty and doubts about the real need to vaccinate children against Covid. of this age.

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I think it is right to vaccinate also to protect one

Clearly, I am among those who think it is right to also vaccinate all children in order to protect one a year from death but I would like to have a really effective vaccine against the infection, certainly not the one we have available now against the virus we have now. .

From a public health perspective, the risks and costs of vaccination, it is necessary to take into account that children of 5-11 years old become infected very easily, the infection occurs in the vast majority without or with few symptoms but equally generates a robust and lasting immune response, much more than in adults, which naturally protects against Covid. And it is not, of course, just a question of Italian children.

The other studies confirm

In a study just published by Israeli researchers on the New England Journal of Medicine, out of nearly 200,000 children aged 5-11, with Omicron as the dominant variant, there were 3 hospitalizations, 2 in unvaccinated and one in vaccinated. In another, earlier study, at the time of the Delta variant, also by Israeli researchers, of nearly 300,000 unvaccinated children and adolescents, there were more than 200,000 infections, more than 80 percent of which were symptom-free, 50 hospitalizations and no deaths within a 6 month period. Yet the children were protected for a long and long time (up to 18 months) from re-infections.

Vaccines are used to go to school, play sports and more

Clearly, vaccines do not only serve to avoid a serious disease, their benefit must also be seen from an educational and social perspective: if protected from infection, children can go to school, play sports and other activities together, without transmitting the virus to others. In our case, all this collides with a vaccine that today protects very little from infection (less than 30% the two doses, perhaps even less than this percentage against the sub-variants of BA.2, and which can also infect subjects who have overcome the Omicron BA.1 infection. the dominant one during the experimentation done by the ISS.

Identify the most appropriate vaccination strategy

In conclusion, the evolution of the pandemic and the foreseeable scenarios of the near future regarding the prevention and control of infection and disease in children must be carefully considered. It is necessary to study what could be an adequate vaccination strategy for them in a time of rapid evolution of the virus, low vaccine protection against its transmission, high susceptibility to infection but low incidence of severe forms and the clear reinvigoration of the pandemic we are already observing.

*Membro dell’American Academy of Microbiology

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