Adam Finn is a senior clinician in pediatric immunology and infectious diseases at Bristol Royal Hospital for Children in Britain and a professor of pediatrics at the University of Bristol. Richard Malley is a pediatrician specializing in infectious diseases and a professor of pediatrics at Harvard Medical School.

In March, three months after its coronavirus vaccine was authorized in the United States and Europe, Pfizer and BioNTech reported the successful results of a trial in adolescents. The companies also initiated studies in children as young as 6 months old. Vaccine maker Moderna has also performed studies in adolescents and younger children.

On Monday, the Food and Drug Administration granted authorization of Pfizer-BioNTech’s vaccine for 12- to 15-year-olds. An application for children ages 2 to 11 may be forthcoming in September.

Speaking as pediatricians who are also vaccine researchers, we say: Please don’t make a priority of immunizing healthy children 2 to 11 years old against the coronavirus.

Our opposition shouldn’t be misinterpreted as a lack of confidence in the vaccines. They are extremely effective — and are desperately needed in large parts of the world by those who are most vulnerable to covid-19.

With effective vaccination programs well along in the United States, Britain, Israel and elsewhere, the impulse to keep lowering the targeted age categories until entire populations have been largely vaccinated is understandable.

But in the United States alone, there are nearly 50 million children 11 and younger. Meanwhile, crematoriums are working around the clock in India. Overwhelmed hospitals are running out of oxygen in Brazil. Many poorer countries have yet to receive a single vaccine shipment. In this context, it is difficult to justify using limited vaccine supplies to immunize young, healthy children at little risk of severe disease from covid.

There is a clear humanitarian and ethical imperative to use available vaccines to try to reduce deaths and hospitalizations everywhere, not just in wealthy countries.

Ethical arguments aside, the fact remains that the greatest threat to children in countries with well-advanced vaccine programs comes from areas where covid remains highly prevalent. This risk is compounded by the emergence of strains potentially capable of escaping vaccine- and infection-induced immunity.

Whether vaccines will prevent severe disease from variants is still unknown, though there have been encouraging signs; letting novel strains of the virus emerge and be disseminated across the globe is definitely not the best way to find out.

The best way to fight the pandemic is with a global campaign to vaccinate those most at risk of occupational exposure and serious disease, including the elderly and people with certain chronic conditions.

As vaccination programs work their way through younger cohorts, the number of people needed to be vaccinated to prevent a death rapidly climbs. By the time young children are being considered, there are almost no deaths to prevent and only very small numbers of hospitalizations.

At that point, the rationale behind mass immunization shifts increasingly toward indirect protection, or herd immunity. With growing evidence that coronavirus vaccines prevent asymptomatic infection and onward transmission, an argument used to justify immunizing young children is that it would mean reaching herd immunity faster.

That approach can be useful with influenza or pneumonia, because children play a large role in their transmission. But young children do not appear to be important transmitters of covid. Population-based studies in Iceland showed that children younger than 10 were far less likely to be infected with the virus or transmit it to others. Similar results were found in Israel.

More research will be needed to confirm those studies, but the real-world evidence is compelling. Consider that in Israel, more than 60 percent of the adult population had received the Pfizer vaccine by last month, and covid had been virtually eradicated. There was a 98 percent reduction of covid in all age groups, yet no child under age 16 had been vaccinated.

The Israeli example ought to prompt fresh thinking about how to achieve herd immunity. Much discussion has focused on the percentage of individuals needed to be vaccinated to reach herd immunity, with most estimates in the range of 60 to 70 percent. Instead, the focus should be on those who are the most likely to transmit the virus; in the United States, with much of the elderly population vaccinated, that means young adults.

The universal vaccination of healthy children 2 to 11 years old simply shouldn’t be a priority and may ultimately prove unnecessary. The relatively small group of children at risk because of underlying medical conditions should of course be offered the coronavirus vaccines, once they have been established as safe and effective for that age group.

For that reason, the pediatric vaccine trials should be completed, so that immunization would be available for especially vulnerable young children. Otherwise, those tens of millions of vaccines can be put to much better use elsewhere in fighting the pandemic.

On May 12, the CDC's Advisory Committee on Immunization Practices, after briefings by CDC, voted to make Pfizer's Covid vaccine available to all 12 to 15 year olds in the US.