It’s complicated — Amid pathetic uptake, FDA green lights confusing COVID vaccine update for kids <5 Some kids can get boosters, some can get an updated series, some get nothing.

Beth Mole – Dec 9, 2022 11:08 pm UTC Enlarge / Reisa Lancaster RN, left, administers the Covid-19 vaccine to 14 month old Ada Hedge, center, being comforted by mom Sarah Close and dad Chinmay Hedge, right at Children's National Research and Innovation Campus, in Washington, DC. Getty | The Washington Post, Bill O'Leary reader comments 35 with 0 posters participating Share this story Share on Facebook Share on Twitter Share on Reddit

The Food and Drug Administration has greenlit updated COVID-19 vaccine doses for children under the age of 5, but the change to the authorized vaccination regimens is far from straightforward. This may further hamstring efforts to vaccinate the youngest Americans, which are already off to an abysmal start.

After months of availability, only about 3 percent of infants and toddlers 6 months to 2 years old have completed a primary series. Just 6.5 percent have gotten at least one shot, according to data from the Centers for Disease Control and Prevention. For those aged 2 to 4 years, just under 5 percent have completed a primary series, with 9 percent having gotten at least one dose.

It was back in June when the FDA authorizedand the CDC endorsedsmall doses of both Moderna's and Pfizer's COVID-19 vaccines for children as young as 6 months old. For Moderna's vaccine, infants 6 months to adolescents 17 years could get a primary series of two doses, one month apart. For Pfizer's vaccine, infants from 6 months to children through age 4 years could get a primary series of three doses, the second being given three weeks after the first and the third being given at least eight weeks after the second. (Pfizer's vaccine was previously available to children 5 years old and older.)

This fall, the FDA authorized an "updated" bivalent vaccine for use as a booster dose in people aged 5 years and above. The bivalent shot targets both the original version of SARS-CoV-2 and the coronavirus omicron subvariants BA.4/5, which were dominant during the summer months. Now, genetic offshoots of BA.5 are dominating circulation. Recent real-world effectiveness data suggests that the bivalent booster offers up to 56 percent more protection against symptomatic COVID-19 infection than protection from the original boosters. Advertisement

But until now, children under 5 were stuck with just the original primary series, not boosters or bivalent shots. Whats new for young kids

Thursday, the FDA authorized bivalent shots for children 6 months to 4 years old and the CDC is expected to endorse the authorization soon, opening availability. But the authorizations are a little complicated; it is not a blanket authorization for boosters in this age group.

Only children aged 6 months through 5 years who received Moderna's two-dose primary series are eligible to get a single bivalent vaccine as a booster dose. That booster dose is to be given at least two months after the completion of the primary series.

For Pfizer's bivalent vaccine, there is still no booster available for children under the age of 5.

The FDA did update Pfizer's three-dose primary series to include the bivalent vaccine as the third shot in the series. That means any child in the age range of 6 months to 4 years who has not been vaccinated and starts a Pfizer series or has already begun a Pfizer three-dose series but has not yet completed it can get the bivalent dose as their third dose in the Pfizer three-dose primary series. For example, if a 2-year-old has already received two Pfizer doses and is in the two-month window before their third shot, that toddler will get the bivalent shot as their third dose when their time comes. Similarly, any child who now starts the Pfizer three-dose series will end with a bivalent shot as their third dose.

But for any children under 5 who already completed the original three-dose Pfizer series, this week's update does not offer them eligibility for a bivalent shot or booster. The FDA said that a bivalent booster could come early next year for this group, though. Advertisement

"Children in this age group who already completed their [three-dose Pfizer] primary series would still be expected to have protection against the most serious outcomes from the currently circulating omicron variant," the FDA said Thursday. "The data to support giving an updated bivalent booster dose for these children are expected in January. The agency is committed to evaluating those data as quickly as possible." Vaccination coverage

The complicated nature of the update does not bode well for spurring uptake of bivalent shots for this young group, which has already seen low uptake. That's despite signs of upticks in COVID-19 cases and hospitalizations, as well as an ongoing crush of seasonal respiratory illnesses, such as RSV and flu, that are overwhelming US hospitals and hitting young children particularly hard.

This week's update "wont have a lot of real-world impact," Peter Hotez, a professor of pediatrics and molecular virology and microbiology at Baylor College of Medicine, told the Washington Post Thursday. "Its like arguing over how many angels can dance on the head of a pin."

But the FDA is still urging more protection for the youngest.

"More children now have the opportunity to update their protection against COVID-19 with a bivalent COVID-19 vaccine, and we encourage parents and caregivers of those eligible to consider doing soespecially as we head into the holidays and winter months where more time will be spent indoors," FDA Commissioner Robert Califf said Thursday. "As this virus has changed and immunity from previous COVID-19 vaccination wanes, the more people who keep up to date on COVID-19 vaccinations, the more benefit there will be for individuals, families, and public health by helping prevent severe illnesses, hospitalizations, and deaths." reader comments 35 with 0 posters participating Share this story Share on Facebook Share on Twitter Share on Reddit Beth Mole Beth is Ars Technicas health reporter. Shes interested in biomedical research, infectious disease, health policy and law, and has a Ph.D. in microbiology. Email beth.mole@arstechnica.com // Twitter @BethMarieMole Advertisement Channel Ars Technica ← Previous story Related Stories Today on Ars