In many rich countries, anyone who wants a COVID vaccine can get one — except for the youngest kids aged 2-4 years. Here are a few potential reasons why.

The science on COVID-19 vaccines for kids under 12 still needs work. That's the basic conclusion you can draw from a range of studies and clinical trials published over the past few months.

Take this study into the BioNTech-Pfizer COVID vaccine.

In a pre-print published in February, researchers suggested that the vaccine provided almost zero protection against infection for children between 5 and 11 years of age.

The researchers had conducted their study between mid-December 2021 and the end of January 2022. That was during the height of the omicron surge of the coronavirus.

They found that the vaccine's ability to protect kids against infection dropped from 68% to 12% over the course of that time. In adolescents, protection fell from 66% at the start to 51% by the end of the study — say the researchers.

When it came to preventing serious infections, the vaccine's efficacy appears to have been more stable.

Its ability to reduce the risk of hospitalization for children aged 12-17 years fell from 85% in mid-December to 73% in late January. For the 5 to 11-year-olds, the number dropped from 100% to 48%.

The data are "not surprising," write the researchers. The BioNTech-Pfizer vaccine was developed for an earlier COVID-19 variant, they say, and similar results have been found "to some degree" in trials with other vaccines, where kids of the same ages also got two doses.

Different vaccines, different doses

The study offers a striking insight into the efficacy of the BioNTech-Pfizer vaccine among kids of very similar ages.

Among the 11-year-olds in the study, the vaccine's efficacy was 11% at the end of January. But among the 12-year-olds, its efficacy was still much higher at 67%.

The reason for that large difference "could be due to dosage," write the study authors.

The 11-year-olds got two 10 microgram doses of the vaccine. And the 12-year-olds got two 30 microgram doses — that's one year's age difference, and three times the dose.

Just to compare, Moderna has opted for a 50 microgram dose of its vaccine for 6 to 11-year-olds. That is exactly half the dose of its vaccine for adults.

The study offers a striking insight into the efficacy of the BioNTech-Pfizer vaccine among kids of very similar ages.

Among the 11-year-olds in the study, the vaccine's efficacy was 11% at the end of January. But among the 12-year-olds, its efficacy was still much higher at 67%.

The reason for that large difference "could be due to dosage," write the study authors.

The 11-year-olds got two 10 microgram doses of the vaccine. And the 12-year-olds got two 30 microgram doses — that's one year's age difference, and three times the dose.

Just to compare, Moderna has opted for a 50 microgram dose of its vaccine for 6 to 11-year-olds. That is exactly half the dose of its vaccine for adults.

What about vaccines for the really little ones?

Last September, Pfizer said it was working on a vaccine for children aged between 2 and 4 years.

The company's CEO Albert Bourla said they would have data on the effectiveness of a two-dose, 3 microgram shot by the end of 2021. They said they would also be ready to begin regulatory approval processes.

But when that data became available in December, Pfizer said it wanted to take the study further and look at the effects of a third dose.

Why is it taking so long?

When the vaccine was first developed, most scientific attention was focused on measuring effectiveness in people who experienced the worst illnesses from the virus. That included older people and those whose immune systems were compromised because of an existing condition. It did not include children.

Children were not experiencing the same serious effects of the virus as adults, and that made kids a lower priority.

Little kids, unlike adults, just don't get very sick from COVID, said Hübner. "It does happen," he said, "but it's rare."

Before the omicron variant became dominant, says Hübner, he saw one child every couple of weeks. Now that number has increased to around five or six at a time. But the children are all in normal wards, he says. None of them need intensive care.

Parental attitudes to vaccination

Some of the parents he sees are anxious to vaccinate their kids as soon as possible, says Hübner, but that's not how the majority of parents feel.

Vaccine acceptance among parents who have children aged between 5 and 11 years is lower than general vaccination rates among older people — just 17% of kids get vaccinated. Even among German adolescents, only around 28% are fully vaccinated.

But Hübner says the low vaccination rates are not a big deal.

"I think for the kids, it doesn't matter," he said. "If you want to protect the population from COVID, you need to vaccinate adults because they are the ones who get seriously sick. For the kids, it's not as important."

However, if your child is immunocompromised or lives with someone who has a high risk due to an existing condition, says Hübner, it is a different story. Those kids should definitely get vaccinated.

Although the risk that they would get very sick themselves is small, Hübner says he would vaccinate his own small kids and recommend his patients do the same.

From Deutsche Welle Newsfeed