When Dr. Joshua Ishal last week in Queens gave his 5- and 7-year-old daughters their first doses of the Covid-19 vaccine, joined millions of other parents in protecting their 5–11-year-old children since the Het Pfizer -BioNTech vaccine was approved for this age group in late October.
dr. Ishal, a dentist living in Great Neck, NY, has never questioned whether to vaccinate his children, but has doubted the timing of their second injections.
The clinical trials that tested the Pfizer vaccine separated doses by three weeks, which is why the US Centers for Disease Control and Prevention recommends that interval. But emerging data suggests that a longer wait boosts the immune response in the long run. In addition, the extra time may reduce the risk of myocarditis — heart inflammation — a rare but serious side effect of the mRNA vaccines in adolescents and younger adults.
Health authorities in Canada recommend that children wait at least eight weeks between doses. In Britain, children wait 12 weeks for the second injection.
Still, the potential benefits of waiting for the second dose must be weighed against the real risks of contracting and spreading Covid while waiting. With the United States on the brink of another major wave of cases and the new Omicron variant spreading rapidly, delaying it means children will remain vulnerable to infections and disease for longer.
“I think that’s a tough decision,” said Aubree Gordon, an infectious disease epidemiologist at the University of Michigan School of Public Health.
Is it more important that children have good protection earlier? Or later better, more durable protection? The riddle makes Dr. Ishal think of an episode of Seinfeld where Jerry tells a story about picking a cold medicine from a wall of options at the drugstore. “This is quick action, but this is long-term,” Jerry said. “When should I feel good, now or later?”
Trish Johnson, a financial advisor in Oakland, plans to cut her son’s second dose down to six or even eight weeks. She is convinced, she said, by the studies showing that a longer interval between doses leads to a better immune response.
“I’ve taken it upon myself, especially during this latter part of the pandemic, to follow doctors on Twitter and do my own research,” she said. Nearly two years after the pandemic, she believes public health officials are taking too many precautions and not adapting to changing data. “That doesn’t work for me anymore,” she said.
Many experts agree that three weeks between doses is too short an interval for an optimal immune response.
“From an immunological standpoint, it makes more sense to wait,” said Deepta Bhattacharya, an immunologist at the University of Arizona. Pfizer didn’t choose three weeks between doses because it was the perfect interval. That decision, he said, “had more to do with public health and reducing community transmission, and completing this process quickly.” dr. Bhattacharya plans to delay a second dose for his children until eight weeks.
The immune system needs time to get going after that first dose. Immune cells in the blood, also called B cells, can start producing antibodies within a week. But to generate really high-quality antibodies, those cells have to go through an intensive kind of training camp in the lymph nodes, and that process takes more than three weeks.
“You need them to sweat a little, those B cells,” says Andrés Finzi, an immunologist at the University of Montreal.
Much of the research on different dosing intervals comes from countries, such as Canada and Britain, that chose to wait for the second adult injection when vaccine doses were scarce last winter and spring. dr. Finzi and his colleagues examined the immune response in 26 people who received their second injection three months or more after their first. They also looked at the reactions of 12 people who received their injections four weeks apart. The two groups produced about the same amount of antibodies, but the group with a longer interval between doses produced stronger antibodies with a greater ability to attach to the virus and stay there.
In Britain, officials last December extended the dose interval for all vaccines to 12 weeks. Researchers from the University of Oxford studied hundreds of health professionals who received a second dose before or after that policy went into effect.
Their study found that people who waited 10 weeks between their first and second dose had about twice as high antibody levels as those who waited just three or four weeks. Those antibodies are produced by B cells, which continue to develop over that long interval.
“It seems that giving the second dose after three to four weeks is just a little too early for your B cells to be ready to get that boost,” says Susanna Dunachie, an immunologist at the University of Oxford who has been diagnosed with the disease. led the investigation. In addition, the longer dose interval also affected T cells, which help ramp up the body’s immune response. After the long interval, the study participants’ T cells produced higher amounts of interleukin-2, a chemical signal that aids long-term immune memory.
“We were quite surprised,” said Dr. dunachie.
However, she added that a stronger immune response measured in the lab would not necessarily lead to better protection in the real world.
The coronavirus pandemic: important things to know
At this point, the results are mixed. Surveillance data from British Columbia and Quebec suggest that a longer dosing interval improves vaccine effectiveness, according to a study not yet peer-reviewed. That is, people who had a longer period between doses had a lower risk of getting infected than those who chose less time.
But studies from Britain weren’t so clear. A modest benefit of delaying the second dose was found. Two other studies found no effect.
The impact of dosing intervals on the risk of myocarditis is even less clear. In one study, not yet peer-reviewed, researchers reviewed vaccine safety data in Ontario and identified 297 cases of inflammation of the heart muscle, or the outer layer of the heart, after vaccination in people 12 years and older. Of these, 207 occurred after the second dose. The rates were higher in people who took their vaccines a month or less apart compared to those who waited six weeks or more.
Whether the vaccine will cause excessive myocarditis in 5- to 11-year-olds remains to be seen. So far, more than seven million doses of the vaccine have been administered to this age group in the US and only 14 possible cases of myocarditis have been reported to the government.
The risk of myocarditis is much higher in teenage boys and young men: according to one study, about 11 cases in every 100,000 men between the ages of 16 and 29 who receive a second dose.
That worries Lisa Rollins, a software trainer in Fredericksburg, Virginia. Her son turned 12 in early December after receiving his first dose. She plans to wait six weeks to give him his second shot. He is now doing virtual learning, she and her husband are working from home and the rest of the family is fully vaccinated. So “his risk is pretty low,” Ms. Rollins said. “I think it makes sense for us to wait a little longer.”
Scott Hensley, an immunologist at the Perelman School of Medicine at the University of Pennsylvania, points out that we also can’t quantify how much benefit children can benefit from waiting a few weeks. His children received their second dose four weeks after their first.
“If there wasn’t a pandemic going on, the answer would be simple — longer duration would be better,” said Dr. hensley. But “we’re at a point in time in the United States where Omicron is going to sweep our nation and it’s probably going to be sweeping the world. And so there has never been a better time to get vaccinated.”
It is an argument that Dr. Ishal increasingly convincing. The number of cases is rising in New York City. The city-run vaccination site in Queens, where he took his daughters for their first injections, booked second dose appointments for three weeks. Considering what’s happening to Omicron, he might be holding that timeslot.
“We’ll take all the protection we can get now,” he said. “I think I’ve just decided.”