January 10: The Moderna vaccine for kids ages 2 to under 5 could be available this spring, possibly in advance of the Pfizer vaccine for the same age group. Dr. William Hartman, the principal investigator of one of Moderna’s pediatric Covid vaccine trials, told Los Angeles Times he believes that FDA emergency use authorization for kids under 5 could come as soon as the end of March or early April.

Dr. Hartman expects to have initial data on the clinical trial results for this age group within the next month. He told LA Times it’s “highly possible” that Moderna will reach authorization before Pfizer does, as the most recent Pfizer trial data in December did not show an adequate immune response against the virus in the 2-years to under-5-years age group. 

In Pfizer’s trials, the dosage for kids aged 2 to 4 is set at one-tenth of the Pfizer adult dose in a two-shot regimen. Pfizer is now currently testing a three-shot vaccine regimen at the same dosage in kids ages 2 to 5 to see if it produces a stronger antibody response.  

The Moderna pediatric trials are being conducted with a higher dose, at one-quarter of the Moderna adult dose. Dr. Hartman says a two-shot regimen of that dosage is proving both safe and effective in study participants “as far as we can tell,” he tells LA Times

According to the most recent reports from The American Academy of Pediatrics (AAP), more than 1 in 10 children have now tested positive for Covid since the pandemic began nearly two years ago. And with the highly contagious Omicron variant circling in all parts of the country, we're seeing not only a rise in cases but a rise in hospitalizations. Though it still appears at this time that severe illness is rare among children, they are still getting infected.

Pfizer's Covid vaccine for 2- to 5-year-olds did not produce a strong immune response

December 17: In clinical trial data released on Friday, a 3-microgram dosage of the Pfizer-BioNTech vaccine did not produce an adequate immune response in kids ages 2 to 5 to effectively defend against Covid. The companies announced they will now continue their clinical trials, testing a three-dose vaccine regimen for kids in the 6 months to under 5-years-of age group.

The trial results showed that after two doses of the 3 mcg shot, which is one-tenth of the adult dose, children between the ages of 6 months to 2 years had a robust immune response comparable to that of 16- to 25-year-olds. However, kids between ages 2 and 5 did not mount a similarly strong immune response.

This is certainly a setback for many parents who were hoping for streamlined access to vaccine protection for kids under 5, who are still vulnerable to the virus. Extending the trial could mean that shots may be further out than originally thought. The companies announced that they plan to seek FDA authorization in the first half of 2022.

Rather than testing a higher dose of the vaccine in the 2 to 5 age group, the companies will seek approval for the three-dose regimen, with kids receiving a third shot at least two months after their second shot. Whether kids ages 5 to 11 need a third dose is also being investigated.

Updates on the timeline for Pfizer's Covid vaccine for kids ages 2 to 5

December 1: Now that Pfizer’s Covid vaccine has been approved for emergency use in children ages 5 to 11 and more than 4 million kids in that age group have now received at least one shot, many parents of younger children are wondering when a vaccine will be made available for kids under age 5.  

According to a public presentation on Pfizer’s third-quarter 2021 earnings, the company highlighted key goals and target dates that might give us a clue as to the timeline. 

As updates come in, we'll keep you in the loop here.

In a chart featured on slide 29 of the presentation, Pfizer outlines potential dates for regulatory approvals and data readouts of results from their drug trials. The chart highlights the fourth quarter of 2021 for when the company expects to present data on the vaccine trials for kids between the ages of 2 and 5 (listed as “key pivotal readouts” on the chart). That’s the end of this year.

For regulatory approval of shots for that age group, as to when the company would apply for authorization from the Food and Drug Administration (FDA), Pfizer is looking at the first half of 2022. That could mean shots may be available in spring or early summer of 2022 for kids ages 2 to 5. 

When will vaccines be available for kids ages 6 months to 2 years?

For kids under 2, Pfizer expects to have initial trial data ready to present in the first half of 2022. The company expects regulatory approval for the vaccine for younger children to then be available in the second half of 2022. That’s looking like late summer or early fall at the earliest for this younger age group.

These internal deadlines are not strict deadlines set by any outside agency, of course. Earlier estimates from experts had posited that shots for the under-5 age group might be available by the end of 2022, but it seems like that’s no longer the case.

Why are shots for kids under 5 taking so long?

Pfizer is the furthest along of the group of three vaccine makers in clinical trials for this age group, though Moderna is expected to apply for authorization soon for its pediatric vaccine for kids ages 5 to 11. 

But what’s taking so long? Pediatric trials can happen only after a vaccine is already deemed safe and effective in the lab, then in animals and finally in adults, says Dr. Fataneh Majlessipour, a pediatric oncologist at Cedars-Sinai in a blog post. Pediatric trials are often the last to begin, after vaccines are determined to be safe and effective in adults and older children, and approved by various regulatory agencies.

One factor that has delayed the studies for children under 5 is that it takes time to deduce what dose will be safe and also produce a robust antibody response in younger kids, who tend to have a more powerful immune response in general. Some research points to stronger immune function being connected to the other routine childhood vaccines kids receive from a young age. 

The FDA also asked both Pfizer and Moderna to expand their trials in order to account for concerns about myocarditis, a rare type of heart inflammation. In Pfizer’s trials in kids ages 5 to 11, no cases of myocarditis were found in the more than 2200 participants. According to the The American Academy of Pediatrics (AAP), myocarditis risk is 37 times higher in kids with Covid than in kids of the same age who haven’t been infected. 

Kids still make up a large portion of Covid cases

COVID cases among children remain extremely high: For the 16th week in a row child COVID-19 cases are above 100,000. Nearly 132,000 cases were reported just the week of Nov. 25. 

Kids under 5 are currently the only subset of the population who are still ineligible for vaccination, making them a primary target (along with anyone else who is unvaccinated) for the virus. And the virus certainly isn’t stopping anytime soon. With the news of the latest Covid variant of concern, Omicron, circulating around the world, President Biden, Dr. Anthony Fauci and the White House Covid Task Force are urging everyone who is eligible to receive a Covid vaccine or a booster if they were vaccinated more than 6 months ago. 

The Centers for Disease Control and Prevention (CDC) recently changed its language on booster shots, now recommending them for all adults over the age of 18. Pfizer is also currently applying to the FDA to authorize boosters in 16- and 17-year-olds. 

How to protect kids under 5 from getting Covid

There are more than 25 million children in the under-5 age group, which accounts for a large portion of the population that’s still highly susceptible to infection.

While we wait for vaccine trials to complete and agency approval to commence, here's what you can do to keep your kids safe:

  • Keep up with kids' masking if they’re over 2
  • Regular hand-washing
  • Practice social distancing
  • Avoid public places or large gatherings
  • Utilizing frequent testing before and after events and if your child shows any symptoms of the virus.

These are all measures that can help curb the spread of the virus and protect your child. Additionally, keeping your child up to date on their other routine vaccinations and getting a flu shot can also help lend some immune benefits. But the most effective thing you can do? Encourage vaccination and booster shots for any and all teens and adults in your orbit.

A version of this post was originally published on Dec. 1, 2021. It has been updated.