A better way to measure immunity in children

For Jacqueline Almeida, next week cannot come anytime soon.

She looked at her friends with wide eyes when she asked to meet them outdoors. She tried to convince her sister to vaccinate her son but failed. Strangers on Twitter say that giving her daughter a mask is tantamount to child abuse.

However, vaccines for the youngest Americans face delays. Ms Almeida, 33, of Franklin, Tenn, said: ‘It’s been disappointing, month after month, to see things get pushed around.

But now there’s some good news: The vaccine will be available within days for her 6-month-old son and 2-year-old daughter. Scientific advisors to the Food and Drug Administration on Wednesday recommended the Pfizer-BioNTech vaccine for children 6 months to 4 years old and the Moderna vaccine for children 6 months to 5 years.

It was the agency that authorized the vaccination on Friday, and the Centers for Disease Control and Prevention is likely to follow suit on Saturday. If all goes according to plan, about 18 million children in this age group will be eligible for the first time being immunized against the coronavirus, the final piece of the nation’s vaccine strategy.

However, after a series of delays by regulators, only about a fifth of parents plan to have their young children vaccinated right away, according to a recent survey.

In a letter to FDA officials in April, nearly 70 scientists made their own assessment: Delays are preventable. Their argument is a technical one, but has broad implications.

The agency and manufacturers chose to evaluate the vaccine by monitoring antibody levels in the blood, the scientists said. But if regulators also looked at other parts of the immune system, it might soon become clear that vaccines could prevent serious illness, if not infection, in young children.

In particular, the scientists argue, vaccine makers should have measured so-called T cells, which can kill infected cells and clear the body of the virus. “That could allow us to make a different decision about allowing a vaccine to be released,” said John Wherry, director of the Institute of Immunology at the University of Pennsylvania and one of the signatories of the letter. develop earlier.

“If we’re not measuring T cells, we’re missing out on a big part of what’s happening,” he added. “Oh my, we’re 18 months old, we can devote a little bit of energy to that sort of thing at this point.”

The FDA declined to comment on the letter, but Dr. Wherry said agency officials called the scientists about a month ago to discuss their ideas.

Vaccine manufacturers have conducted large trials to measure the vaccine’s effectiveness in preventing symptomatic infections in adults. But in the children’s trials, investigators looked at blood levels of antibodies after vaccination, comparing them with those seen in young adults.

The FDA has used this approach, called immunoconjugation, to license the Pfizer-BioNTech vaccine for children 5 to 11 years of age and for adolescents 12 to 15 years of age. But in December, the companies reported that two doses of their vaccine did not produce high levels of antibodies in children aged 2 to 4 years.

The companies decided to evaluate whether the third dose would improve the vaccine’s performance. Then, over the winter, some of the infants in the clinical trial were infected with the Omicron variant.

Based on preliminary data from those infections, the FDA said it would consider licensing two doses of the vaccine while the companies continue with a third trial — a decision that has drawn mixed reactions from the public. parents and professionals.

But the growing number of infections in children, and accumulating data that did not support the FDA’s decision, prompted the agency to cancel the planned review. The back and forth left parents confused and their children vulnerable, as Omicron variants raged across the country.

The CDC reported in April that about 75% of children may have been infected with the coronavirus by March, many of them during the Omicron surge. The number of children hospitalized is a record, although still much lower than that of adults.

More information about the T-cell immunity generated by vaccines could help desperate parents get vaccinated earlier and prevent at least some hospital admissions, experts say , experts said in interviews.

Antibodies are essential for neutralizing invading viruses and preventing infection, and they can be easily measured in just a drop or two of blood. But while there are dozens of rapid tests for antibody levels, a T-cell assessment requires at least a few milliliters of blood and at least a few samples a day.

Camille Kotton, an infectious disease physician at Massachusetts General Hospital and scientific adviser to the CDC, said:

“It’s never as easy as the antibody, but it certainly helps,” she said.

And not everyone believes that T cells are an important measure of immunity. Dr Miles Davenport, an immunologist at the University of New South Wales in Sydney, said low levels of antibodies could be enough to prevent severe illness.

Dr Davenport said: “There are no studies to demonstrate that the level of T cells produced by the vaccine predicts the risk of infection or the risk of severe disease.

However, epidemiological data indicate that even with a decrease in antibody levels and a sharp increase in infections, hospitalizations and deaths among vaccinated individuals remain relatively low. That suggests that something other than antibody levels protected people from severe illness, Dr. Wherry said.

He added: “Death rates only increase in the very old or the immunocompromised, where we are deficient or have a poor T-cell response. “There’s a lot of good case data out there, but we’re really missing a smoke gun.”

A new initiative at the University of Pennsylvania may yield some answers. Called the Immune Health Project, the study will simultaneously assess antibody and T-cell responses in immunocompromised patients after vaccination.

Unanswered questions about childhood immunity may explain why about 40% of parents with young children are hesitant about vaccinations: Less than 30% of children aged 5 to 11 have been given two doses and the need for the youngest may be even lower .

Monica Lo, 35, an assistant principal at a Seattle school, was one of those hesitant. “Vaccines for covid are happening so fast and so fast that we want to give it a little more time,” she said.

Lo and her husband are both fully vaccinated, but their 7-year-old son, Gian, received only one shot in January before his scheduled trip to Hawaii. They decided to delay his second dose because the data showed that doing so could induce better immunity, Ms. Lo said.

The couple also have a 2-year-old daughter and Ms. Lo is pregnant with their third child, expected in July. But they have no plans to vaccinate their daughter yet, Ms. Lo said. won’t be the first in line.”

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