Covid vaccine elicits strong immune response in younger children, says Pfizer


The Pfizer-BioNTech coronavirus vaccine has been shown to be safe and highly effective in young children ages 5 to 11, the companies announced early Monday morning. The news should help alleviate months of anxiety among parents and teachers about when children, and their close contacts, may be protected from the coronavirus.

The need is urgent: Children are now responsible for more than one in five new cases, and the highly contagious Delta strain has sent more children to hospitals and intensive care units in recent weeks than at any other time in the pandemic.

Pfizer and BioNTech plan to file an application with the Food and Drug Administration for authorization to use the vaccine in these children by the end of the month. If the regulatory review goes as smoothly as it has with older children and adults, millions of elementary school students could be vaccinated before Halloween.

Study results for children under age 5 aren’t expected until the fourth quarter of this year at the earliest, according to Dr. Bill Gruber, senior vice president at Pfizer and pediatrician.

Pfizer and BioNTech released the results in a statement that did not contain detailed data from the trial. The findings have not yet been peer-reviewed or published in a scientific journal.

But the new results align with those seen in older children and adults, experts said.

“There will be a huge number of parents who will breathe a sigh of relief when they hear this,” says Dr. Kristin Oliver, a pediatrician and vaccine expert at Mount Sinai Hospital in New York. “We’ve been waiting for these children to be protected.”

Children have a much lower risk of Covid-19 than adults, even when exposed to the Delta variant. Yet a small number of infected children develop a life-threatening condition called childhood multisystem inflammatory syndrome or MIS-C. Still others may have persistent symptoms for months.

In August, nearly 30,000 children were hospitalized for Covid; the least vaccinated states reported the highest rates. At Seattle Children’s Hospital, about half of children admitted for Covid are over the age of 12, according to Dr. Danielle Zerr, an expert on childhood infections at the hospital.

“I am baffled that the sickest children in our hospital with acute Covid-19 or MIS-C are children who could have been vaccinated,” said Dr. Zerr.

As ideological battles over masking and vaccine mandates rage in communities, the reopening of schools has fueled the wave. In Mississippi, of the states without a mask mandate, nearly 6,000 students tested positive for the virus in one week, and more than 30,000 students, faculty and staff had to be quarantined.

A South Carolina county — where mask mandates are banned — had to quarantine more than 2,000 students in one day. Distance learning is not an option in many districts, so the safety of some medically vulnerable children in many parts of the country has become subordinate to the actions of others.

Unvaccinated children, even if they don’t get sick themselves, can spread the virus to family members, teachers and others with whom they have regular contact – including grandparents or those prone to serious illness or death.

Wearing a mask and good air circulation can significantly reduce the transmission of viruses. But children are just as likely as adults to transmit the virus according to a recent review of the evidence by the Centers for Disease Control and Prevention.

Pfizer’s trial involved 2,268 children ages 5 to 11, two-thirds of whom received two doses of the vaccine three weeks apart; the remainder were injected with two doses of saltwater placebo.

Given how rarely children become seriously ill, the trial was not large enough to draw meaningful conclusions about the vaccine’s ability to prevent Covid or hospitalization. Instead, the researchers relied on measurements of the youth’s immune response, assuming that the protective levels of antibodies seen in older people would be just as protective in younger children.

The children who received the vaccine produced a strong immune response, similar to the levels of antibodies seen in previous studies involving participants ages 16 to 25. But children in the 5 to 11-year-old group achieved this response with 10 micrograms of the vaccine, one-third the dose given to older children and adults.

At higher doses, the researchers observed more side effects in younger children, including fever, headache and fatigue, although none were serious, said Dr. Gruber. With the dose of 10 micrograms, “after the second dose, we actually see less fever, fewer chills than we see in the 16- to 25-year-olds.”

The immune system weakens with age and the side effects also become milder. This decrease in potency is why most vaccines are administered in childhood — and why a much lower dose is often enough for children, said Dr. Yvonne Maldonado, who led the trial at Stanford University and is president of the American Academy of Pediatrics’ Infectious Diseases Department. Commission.

“You want to get to the sweet spot, where you give the lowest dose that can elicit responses, but also high enough to give you a good, lasting antibody response,” she said.

In children under age 5, just three micrograms — one-tenth the adult dose — are tested in trials and appear likely to be enough, she said.

The full FDA approval of the Pfizer-BioNTech vaccine in August did not include children ages 12 to 15, who are still receiving the vaccine under emergency approval. As for adolescents, the companies will apply for emergency clearance for children aged 5 to 11.

FDA scientists then have to weigh the benefits of the vaccine against the potential for side effects. In rare cases, the vaccine has led to myocarditis, an inflammation of the heart, in young people.

But a large Israeli study, based on electronic health records of two million people aged 16 and older, found that Covid is much more likely to cause these heart problems.

To detect side effects in younger children, in July the FDA asked Pfizer-BioNtech and Moderna to expand their trials to 3,000 children. But based on the company’s talks with the FDA, Dr. Gruber that he believed the agency would give the green light to the vaccine with the data available to date.

Discussions about the vaccine’s risks to children aged 6 months to 5 years are likely to be even more heated than the heated disagreements about immunizing healthy adults or teenagers.

“There are people who don’t really feel like there is convincing data that children under the age of five should be vaccinated,” said Dr. Maldonado.

While most children are spared serious illness after infection, children’s hospitals and ICUs are overflowing, she added: “Why wouldn’t you want to prevent an infection that could potentially put your child in ICU?”

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