Vaccinating children against Covid-19: Is it justified in low-risk scenarios?

As regulators debate whether or not to recommend the Pfizer vaccine for the under-12s, experts in Spain question whether it is needed if contagion rates stay low

A health worker vaccinates a teenager in Valencia.
A health worker vaccinates a teenager in Valencia.Europa Press News (Europa Press via Getty Images)
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The last big decision regarding Covid-19 vaccines – beyond whether a booster shot is needed – is if they should be administered to children under the age of 12. This is what will be discussed by an independent vaccine committee in the United States on Tuesday and what will be addressed by European governments in the upcoming weeks. Scientists from the US Food and Drug Administration (FDA) released a report on Friday analyzing the pros and cons of the Pfizer-BioNTech Covid-19 vaccine dose for children between the ages of five and 12. The report supported authorizing the vaccine on the grounds that the benefits “clearly outweigh the risks.”

This is the study that the independent committee will use to support its final recommendation to the FDA, which tends to follow its advice, even if it is non-binding. Throughout the coronavirus pandemic, decisions made by the US have tended to foreshadow those later made by the European Medicines Agency (EMA). But it is one thing for an agency to approve a vaccine for use and it is another for health authorities in European countries to launch a mass-vaccination campaign, a decision that will likely be based on the incidence rate of the virus.

The 10 microgram dose of the Pfizer vaccine, which is one third of the full-strength shot given to adults, has a clear effect on children: it is nearly 91% effective at preventing illness after two doses, according to Pfizer’s clinical trials. The doubts over immunizing children are not about the effectiveness of the vaccine but rather due to the fact that most children who contract Covid-19 have either a very mild case or are asymptomatic. Scientists at the FDA analyzed if the secondary effects of the vaccine could be more serious than the disease itself, regardless of how rare they may be. Their response was negative. In the report, the researchers argue that the vaccine provides more protection than any possible harm it could cause. But this conclusion is conditioned on the level of coronavirus contagions in the community: the higher the transmission, the stronger the grounds for vaccinating children, and vice versa.

FDA models show that in almost any epidemiological situation the vaccine could prevent between 200 and 250 hospitalizations per million children. It would practically eliminate the risk of Covid-19 among the under-12s: the studies showed that there was not only a significant drop in contagions, but also that cases were much less serious. Of the 1,591 children vaccinated, only three fell ill with Covid-19, all with very minor symptoms. Of the 788 who were given a placebo, 16 contracted the virus, 10 of whom had a fever and more serious symptoms.

The trial did not show any worrying secondary effects, which is to be expected given the relatively small size of the sample. According to FDA data, after the Covid-19 vaccine was administered in the real world, there were 180 cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the fibrous sac surrounding the heart) among the 12-15 age group, and around 200 in the 15-19 population. Scientists from the FDA estimate that around 98 in every million children vaccinated would require hospitalization for these conditions, which almost solely affect boys. Most of these cases can be addressed with a conservative treatment plan without the need for intensive care.

I don’t think recommending mass vaccination is justified in this epidemiological context
Quique Bassat, from the Spanish Pediatrician Society

In a situation where there are high coronavirus transmission rates, more children would be hospitalized for Covid-19 than for myocarditis. But if there is a low incidence rate, the vaccine could lead to more hospitalizations than the disease itself, according to the FDA report. The scientists, however, say that hospitalizations for Covid-19 would be more serious, and support the recommendation to approve the Pfizer vaccine for children. The document concludes: “While benefits of vaccination were highly dependent on Covid-19 incidence, the overall analysis predicted that the numbers of clinically significant Covid-19-related outcomes prevented would clearly outweigh the numbers of vaccine-associated excess myocarditis cases over a range of assumptions for Covid-19 incidence.”

In the context of Spain’s epidemiological situation, where transmission rates have been at a low risk level since October 7, “almost no pediatrician” would recommend vaccination for all children under 12, says Quique Bassat, an epidemiologist and member of the Spanish Pediatrician Society. “With high transmission, the benefits of the vaccine are clearly greater. In a situation like ours, I don’t think this premise is valid. It is fantastic for it to be approved and available if at some point we have to use it. But right now, I don’t think recommending mass vaccination is justified in this epidemiological context,” he says.

Amós García Rojas, the president of the Spanish Vaccinology Society, agrees: “It will depend on the epidemiological situation at the time. If we continue down the good path of [low] contagions, it probably won’t be necessary, but if it rises a lot perhaps we will. We will have to assess it moment by moment.”

According to the latest figures, released on Monday evening by the Health Ministry, the 14-day cumulative number of cases per 100,000 inhabitants now stands at 46.38. This is a rise of nearly two points since Friday, but still below the 50-threshold considered to indicate a situation of low risk.

A health worker vaccinates a teenager in Madrid in August.
A health worker vaccinates a teenager in Madrid in August.ISABEL INFANTES (Europa Press)

García Rojas, who is part of the expert team that will advise Spanish authorities on whether or not to vaccinate children, argues that with the current incidence rate, the priority should be administering third doses to the over-70 population and increasing vaccination coverage in developing regions. In Africa, less than 6% of the population is fully vaccinated, compared to 80% in Spain.

Sources from the Spanish Agency of Medicine and Health Products (AEMPS) state that just because a vaccine is approved by the EMA – or the AEMPS itself – does not mean it has to be administered. “The risks and benefits are considered, the secondary effects in the packaging insert are clarified and later health authorities are the ones who have to decide to use it or not in each context,” the sources explain. Parents who want to vaccinate their children, for example, may be allowed to purchase the medication, as happens with other shots that are not included in children’s immunization schedule. Or the vaccine may only be recommended for girls under the age of 12, given that practically no secondary effects have been recorded among them.

The FDA will have to consider all this information on Tuesday when it decides whether or not to approve the Pfizer vaccine for children. In the case that it does, the Centers for Disease Control and Prevention (CDC) will have the last word about whether it should be administered to children. Health authorities in European countries will follow a similar process if the EMA decides to approve the vaccine. Meanwhile, Pfizer is also carrying out a clinical trial on how well its Covid-19 vaccine works in six-month- to five-year-old children, the results of which are expected at the end of November.

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