On December 8, 2022, the FDA extended the authorization for these bivalent boosters to children between 6 months and 4 years old. Young children who complete a primary series with Moderna can get a booster two months after their last shot. Children in this age group who have received one or two doses of the Pfizer three-shot primary series will get a Pfizer booster as their third shot. If they have completed the Pfizer primary series, they don’t need a booster right now. Both vaccines were unanimously recommended by the FDA, so that means that you ultimately can’t go wrong with whichever vaccine you pick. Still, there are some differences between the two. We reached out to experts to help us understand what these differences mean and how to make the best choice for your family.
What Are the Differences Between the Two Vaccines?
The FDA and CDC approval of these vaccines mean that they are both safe for children and effective at protecting kids from the most serious effects of COVID-19. In fact, there are more similarities between the two vaccines than there are differences, especially when it comes to what matters most about the vaccines, says Chad R. Sanborn, MD, pediatric infectious disease physician at Palm Beach Children’s Hospital, part of the Palm Beach Health Network. “Both vaccines present a wonderful opportunity to protect children from COVID-19,” Dr. Sanborn explains. “Both seem to have benefits against hospitalization and severe illness, and the side effect profile of the two vaccines seemed to be similar to, or less severe than, in adults.” Here’s a breakdown of what to know about the differences between these two vaccines.
Dosage
Both vaccines use a smaller dose in young children than they do in adults, teens, and older children. Pfizer’s vaccine is based on a 3 µg dose for kids aged 6 months through 4 years, as compared to a 10 µg for kids aged 5 to 12, and a 30 µg dose for ages 12 through adult. On the other hand, Moderna’s vaccine uses a 25 μg dose for kids aged 6 months through 5 years. This is compared to a 50 µg dose for kids aged 6 through 12, and a 100 μg dose for those aged 12 and up. Besides dosage amount, Pfizer’s vaccine was approved as a three-dose vaccine for the younger cohort, whereas Moderna’s vaccine was approved as a two-dose vaccine.
Dosage Spacing
One primary difference between the two vaccines is how the dosages are spaced out, and how long it takes for a child to become “fully vaccinated” according to current recommendations. Pfizer’s vaccine is given as a series of three shots. The first two shots are given three weeks apart, and the third shot is given eight weeks after the second shot. Moderna’s dosage schedule is based on two dosages, spaced 28 days apart.
Efficacy
Efficacy refers to how effective a vaccine is at preventing infection. According to the available data, Pfizer’s three-dose vaccine was about 80% effective in preventing infection. Moderna’s two-dose shot was 51% effective in preventing infection for kids aged 6 months to 2 years, and 37% effective for kids aged 2 to 6 years. It’s crucial to keep in mind that both of these vaccines prevent serious infection, which is what matters most. Additionally, both vaccines were tested in part during the Omicron period, when vaccine efficacy went down for adults as well. As Moderna’s press release points out, the efficacy of its vaccine in younger kids was similar to efficacy for adults during the Omicron period. Importantly, both vaccines produced strong immune responses in children. Pfizer says that the antibody response seen in children for the vaccine was similar to the antibody response produced by 16- to 25-year-olds who received its vaccine. Kids who received Moderna’s vaccine had similar neutralizing antibody titers as adults who received the vaccine.
Side Effects
Both vaccines produced mild side effects for children, similar to the side effects seen for common childhood vaccines given to babies and young children. Pfizer’s most common side effect was pain at the injection site. In kids aged 6 months to 2 years, 7.4% had fevers after the second dose; in kids aged 2 and up, 4.9% had fevers. Moderna’s vaccine had similar side effects as Pfizer’s, but children were more likely to have fevers after the second dose. Of kids aged 6 months to 2 years, 17% got fevers after Moderna’s shot; 14.6% of kids aged 2 through 5 did as well.
Selecting a Vaccine for Your Child
Most medical experts agree that getting your child vaccinated is the primary goal and that it ultimately doesn’t really matter which vaccine you choose, because both will provide your child with the protection they need. “Both vaccines use similar vaccine mRNA technology and work with similar effectiveness,” says Zachary Hoy, MD, pediatric infectious disease specialist at Pediatrix Medical Group Nashville. “Neither one seems overall better; the determination will most likely be which vaccines are available in your area.” Determining which vaccine you wish to get for your child may come down to convenience, says Dr. Sanborn. “Moderna’s vaccine is given in two doses 28 days apart, so that may be logistically easier than Pfizer’s three-dose schedule over three months,” he explains. But that may change eventually, he says, because Moderna is testing a third dose of their vaccine, which may be available in the coming months. Additionally, if side effects are a concern of yours, you may want to choose Pfizer over Moderna, since the data show fewer fevers in kids who had Pfizer’s shot. However, Dr. Sanborn points out that fevers are a common side effect of childhood vaccines, so side effects like this are to be expected. He also points out that Pfizer’s results are somewhat more efficacious against infection, which might also be appealing to parents. Katelyn Jetelina, PhD, epidemiologist, mom of two kids under 5, and founder of Your Local Epidemiologist, shared her thoughts on her decision process as she prepared to get her children vaccinated. “The option is clear for me and my girls: Moderna,” she said. Her reasoning is that Moderna’s shot takes less time to reach full protection—six weeks, as opposed to 18 weeks in total for Pfizer. “The sooner my girls can be protected, the better,” she said. Additionally, Dr. Jetelina points out that Moderna is currently testing an Omicron-specific booster for this age group, which sounds promising to her. She is also skeptical of Pfizer’s 80% efficacy results since the sample size was so small. “The evidence for how well the Pfizer three-dose vaccine works is murky,” she points out. “While it has a high efficacy rate (80%), the scientific confidence in this number is low given the low number of events in the clinical trial.” Other parents are feeling more drawn to the Pfizer vaccine. Conz Preti, an editor and mom of a 4-year-old and 2-year-old twins from Portland, Maine, said that she chose Pfizer for her kids for a few key reasons. First of all, she and her husband got the Pfizer vaccine and had minimal side effects. She liked that reported side effects from the trial in kids were low and that the efficacy of Pfizer’s vaccine appeared higher than Moderna’s. But most of all, Preti picked the vaccine because it was the one first available in her area. “The only place vaccinating [kids] under 3 had Pfizer and we wanted all three kids to get the shot at the same time, and ASAP,” Preti says. “After having pandemic twins, I needed to get them vaccinated the second it was available.” Above all, Dr. Sanborn emphasizes that there is no “right” way to go when it comes to picking one vaccine over the other, and agrees that getting whichever is available first makes sense. “Whichever vaccine a parent can access in their local area would be a good one to get,” he says. “I would recommend either of the two vaccines to a parent.”
If You Are Hesitant to Get Your Child Vaccinated
It’s understandable that parents of little ones might feel some hesitation about COVID-19 vaccines, especially since they may have heard that infections from COVID-19 are generally mild in children. But it’s important to note that this is not always the case, and there have been many young children who have experienced serious cases of COVID-19, and some who have even died from the virus. “The main reason children under five need a COVID-19 vaccine is because COVID-19 is a real threat to children this age,” said Tanya Roman, MD, chief of Pediatrics at Community Health of South Florida, Inc. “As a pediatrician, aside from children who have been hospitalized or died from COVID-19, I have seen children in this age group who have gone on to suffer serious, very real complications from having contracted the virus.” According to the CDC, during the Omicron wave in particular, children under age 0 to 4 years old were hospitalized at five times the rate they were during other COVID-19 surges, including during the Delta variant surge. Dr. Roman believes that some of the more serious threats of the virus have been downplayed and that it’s important for parents to understand that forgoing the vaccine can have potentially dangerous consequences for their child, especially as the pandemic continues. “We just don’t know what getting COVID-19 can ultimately cause as it has been unpredictable,” she says. “But we do know that it’s a serious threat, so it’s especially important to be proactive and have children vaccinated to minimize the chances of serious illness or worse.”
