Should children aged 6 months through 4 years get the Pfizer COVID-19 vaccine?
This article steelmans the two main sides of this argument which we’ll call conventional and skeptical.
First, we’ll summarize the two sides in one sentence each to give a feeling of where we’re going. Next, we’ll list the main justifications. Finally, we’ll dive into the details and citations for those interested.
One-sentence summaries
Conventional: For children aged 6 months through 4 years, COVID may cause serious medical issues including death, the Pfizer vaccine is likely effective in reducing COVID acquisition, its estimated benefits, including reducing community transmission, outweigh the estimated risks of side effects across the population, vaccination may have benefits in addition to natural immunity, vaccination in older groups is associated with reduced deaths, and the burden of proof is on those potentially jeopardizing their children and their community
Skeptical: For children aged 6 months through 4 years that are healthy, risks of COVID-19 may be similar to the flu (influenza virus), the Pfizer vaccine is not likely very effective in reducing COVID acquisition and will likely wane quickly, it is in a new class of vaccines with limited safety data, community benefits are unclear, population-wide risk/benefit calculations do not account for individualized assessments and value judgments, natural immunity is likely robust, and the burden of proof for net benefits is on vaccine providers
Main justifications
Conventional:
COVID is a serious risk for children aged 6 months through 4 years, including death, hospitalization, other diseases such as long COVID, COVID-associated myocarditis & pericarditis and multisystem inflammatory syndrome in children (MIS-C), it may increase disease burden on the community, and vaccination in older groups is associated with reduced deaths.
Pfizer performed a randomized, double-blind, saline placebo controlled trial that showed the vaccine is likely at least somewhat effective and its side effects are likely similar to other vaccines.
The vaccine may help in addition to any natural immunity and may reduce community transmission.
Across the population, the estimated benefits outweigh the known, estimated risks.
Given the above, the burden of proof is on those potentially jeopardizing their children and their communities, including contributing to community spread and hospital utilization.
Skeptical:
COVID risks for children 6 months to 4 years may be similar to the flu (influenza virus).
Getting the vaccine might make sense for those with underlying conditions associated with COVID hospitalization such as obesity, chronic lung disease, asthma, prematurity, neurologic disorder, feeding tube dependency, chronic metabolic disease, diabetes mellitus, blood disorders, sickle cell disease, cardiovascular disease, congenital heart disease, immunocompromised condition, and airway abnormality (Kim et al., 2020; Woodruff et al., 2022).
If vaccinating, take extra care of the children to reduce exposure to COVID-19 between doses 1 and 2.
Why was this Pfizer vaccine study underpowered? The 1954 Fields Trial for the polio vaccine was a randomized, double-blinded, placebo controlled trial with 750,000 children (Juskewitch et al., 2010) whereas the Pfizer study ended with just 1,106 children (U.S. FDA, 2022d; U.S. FDA, 2022e). Probably at least about 20% of parents of children 6 months to 4 years would have volunteered (U.S. CDC, 2022g) which is about 3.7 million children (U.S. CDC, 2022i). Cost shouldn’t be an issue because Pfizer made $36 billion on the vaccine in 2021 and projects $32 billion in 2022 (CNBC, 2022).
Given this vaccine is in “a new class of vaccines” (U.S. FDA, 2022v) and, although rare, the similarly experimental Johnson & Johnson vaccine caused deaths from thrombosis with thrombocytopenia syndrome (U.S. CDC, 2022h), why have Pfizer studies been designed to be underpowered and unblinded shortly after the last dose so that long-term risks can’t be evaluated? There may be biologically plausible concerns about mRNA vaccines (Seneff et al., 2022; Föhse et al., 2021; Lee et al., 2021; Pfizer, 2021; Ndeupen et al., 2021; Igyártó et al., 2021), in addition to impacts of mRNA potentially persisting for two months after vaccination (Röltgen et al., 2022; Fertig et al., 2022) and spike protein potentially circulating four months after vaccination (Bansal et al., 2021), and potential spike protein toxicity (Rhea et al., 2021; Datta et al., 2021; Lei et al., 2021; Raghavan et al., 2021; Fernandes et al., 2022; Suzuki & Gychka, 2021; Pérez-Bermejo et al., 2020; Asandei et al., 2020; Buzhdygan et al., 2020; Biancatelli et al., 2021).
Statistics and estimates across a population do not account for value judgments comparing known actions (vaccination) versus probabilistic events (acquiring a large dose of virus) given individualized risk and benefit estimates.
Given the above, the burden of proof for net benefits, particularly for a new class of vaccines, is on the vaccine providers.
Details and citations
Deaths and hospitalizations
Conventional:
For children through 4 years old in the U.S., COVID as the underlying cause of death (U.S. CDC, 2022j) is estimated to have killed 54 children in 2020, 145 in 2021 (provisional), and 71 in 2022 (provisional through June).
Thousands of children per year through 4 years old in the U.S. have had COVID-19-associated hospitalization (U.S. CDC, 2022), with a relative surge during Omicron (Marks et al., 2022) that was comprised of 85% with COVID-19 as the primary reason for admission (Marks et al., 2022d), 63% with no underlying medical condition (Marks et al., 2022c), and 21% ended up in the Intensive Care Unit (ICU) (Marks et al., 2022b).
Although only correlational, there is an association between vaccination and lower incidence of deaths in ages 5 and up (U.S. CDC, 2022m; Johnson et al., 2022):
Skeptical:
For children through 4 years old in the U.S., COVID-19 has killed fewer children than flu (influenza virus and pneumonia) as the underlying cause of death when comparing annualized rates for 2018-2019 to 2020-2022 (Flaxman et al., 2022; U.S. CDC, 2022j U.S. CDC, 2022k).
The hospitalization rate of COVID for children through 4 years old has been less than flu (Delahoy et al., 2022).
Other potential risks
Conventional:
Infecting others in the community (Schleiss et al., 2021)
COVID-associated myocarditis (Rodriguez-Gonzalez et al., 2020) & pericarditis (Kermani-Alghoraishi et al., 2021)
Long COVID (Wise, 2021)
Multisystem inflammatory syndrome in children (MIS-C) (Chin et al., 2022; Feldstein et al., 2021; Levy et al., 2022)
Acquiring diabetes (Barrett et al., 2022)
Impact of sickness on families (e.g. work) (KFF, 2022)
Skeptical counter-arguments:
Infecting others in the community (Ludvigsson, 2022; U.S. FDA, 2022aa)
COVID-associated myocarditis & pericarditis (Tuvali et al., 2022)
Long COVID (Zimmermann et al., 2022; Zimmermann et al., 2021; Al-Aly et al., 2021)
Multisystem inflammatory syndrome in children (MIS-C) (Yalçinkaya et al., 2022)
Vaccine efficacy
Pfizer performed a randomized, double-blind, saline placebo controlled trial (U.S. FDA, 2022c)
Conventional:
The vaccine effectiveness of avoiding COVID acquisition (at least 6 days after 3 doses):
Children 6-23 months: 75.5% (95% confidence interval of -370.1% to 99.6%) (U.S. FDA, 2022d) with 1 case of COVID in the vaccine group (out of 277) versus 2 cases in the placebo group (out of 139).
Children 2-4 years: 82.3% (95% confidence interval of -8.0% to 98.3%) (U.S. FDA, 2022e) with 2 cases of COVID in the vaccine group (out of 481) versus 5 cases in the placebo group (out of 209.
Vaccine effectiveness is visualized in the cumulative incidence curves (U.S. FDA, 2022l) with the difference red line (placebo) showing higher COVID incidence than the blue line (vaccine); for example, for ages 2-4:
Skeptical:
The results were statistically weak (95% confidence intervals crossed 0) as admitted in the Pfizer report (U.S. FDA, 2022o) and the FDA thought the interpretation of results may be overestimated (U.S. FDA, 2022s).
The results are preliminary (U.S. FDA, 2022p) as the study did not achieve the protocol-specified 21 cases (10 total were observed) and the study is still on-going.
The only hospitalization for severe COVID occurred in a vaccine recipient (U.S. FDA, 2022q) and 6 out of 8 cases of severe COVID (U.S. FDA, 2022x) were in the vaccine group, although the definition of severe COVID was non-standard (U.S. FDA, 2022ah) (i.e. including increased heart rate).
Vaccine effectiveness is only inferred (U.S. FDA, 2022r) based on immunobridging (U.S. FDA, 2022ac) rather than clinically relevant endpoints like death, hospitalization, disease, etc. Immunobridging is comparing antibody levels to those of other age groups that did have clinically relevant endpoints evaluated and guessing that similar antibody levels will mean similar clinically relevant endpoints.
The point estimates between dose 1 and dose 2 were negative (U.S. FDA, 2022ad; U.S. FDA, 2022ae) meaning that the vaccines might be associated with increased COVID as compared to the placebo group.
The vaccine efficacy is likely to wane quickly (U.S. FDA, 2022t).
Adverse events
Monitored for up to 2 months (U.S. FDA, 2022k) after the last dose.
Conventional:
Zero deaths (U.S. FDA, 2022)
Zero potentially life-threatening events (U.S. FDA, 2022m) of grade 4 (U.S. FDA, 2007)
Skeptical:
The FDA judged (Fleming-Dutra et al., 2022b) the “potential harms after vaccination” as “very low certainty […] because of the short duration of follow-up of 1 month after dose 3 and because only 31% of trial participants received dose 3, limiting the ability to detect serious adverse events that might occur at a higher rate after dose 3, and serious concern of imprecision because of the study size.”
There were more severe adverse reactions of grade ≥ 3 (U.S. FDA, 2007) in the vaccine group than placebo: 4.3% vs. 3.6% (Fleming-Dutra et al., 2022).
Some of the serious adverse events were considered by investigators and the FDA as potentially related to the vaccine (U.S. FDA, 2022g).
Some patients were withdrawn (U.S. FDA, 2022h) after adverse events, some of which were considered by investigators and the FDA as potentially related to the vaccine.
Secondary re-analyses of mRNA vaccine trials in adults shows concerning signals about serious adverse events (Fraiman et al., 2022).
Vaccination in addition to natural immunity
Conventional:
In other age groups, for those that were already infected with the SARS-CoV-2 virus and created natural immunity, there is some evidence (Plumb et al., 2022) that vaccines decreased hospitalizations compared to the unvaccinated.
Skeptical:
Natural immunity for children is now likely above 75% (U.S. FDA, 2022u).
There is disagreement (Pugh et al., 2022) about the efficacy of natural immunity with and without vaccination.
The measured antibodies in Pfizer’s study were lower (U.S. FDA, 2022w) against the current Omicron variant compared to previous variants meaning it might be less effective for newer variants.
Benefit/risk calculations
Conventional:
The FDA and Pfizer estimate (U.S. FDA, 2022j) the benefits of vaccination for children 6 months to 4-5 years to be 5,880 fewer cases, 364 fewer hospitalizations, and 5 fewer deaths per million over 6 months.
The FDA and Pfizer estimate (U.S. FDA, 2022j) the known risks of vaccination for children 6 months to 4-5 years to be 2.5 to 74.0 excess cases of myocarditis/pericarditis per million for males and 0.6 to 7.0 for females.
Other pediatric vaccines have been approved for lower disease burdens (U.S. CDC, 2022l).
Skeptical:
Myocarditis and pericarditis are rare but known risks associated with mRNA vaccines (Le Vu et al., 2022; U.S. FDA, 2022y; Chua et al., 2021; Buchan et al., 2022), although ~80% probably fully recover (U.S. CDC, 2022e). Blood was not sampled for troponin levels (Oster et al., 2022) to evaluate the potential of subclinical myocarditis (U.S. FDA, 2022ag).
Anaphylaxis is a rare but known risk associated with mRNA vaccines (U.S. FDA, 2022z). It is particularly difficult (U.S. CDC, 2022c) to recognize in children.
As noted by the FDA (U.S. FDA, 2022v), COVID-19 vaccines “represent a new class of vaccines […] based on new platform technologies”; in the case of this vaccine, rather than a classic vaccine of attenuated or live virus, it is modified mRNA in lipid nanoparticles that enter cells to stimulate protein production, so potential long-term risks are unknown.
Death from vaccination is possible: the CDC determined at least nine deaths were caused by the Johnson & Johnson COVID-19 vaccine (U.S. CDC, 2022h) due to thrombosis with thrombocytopenia syndrome (TTS) (See et al., 2022), although this was an adenovirus-based DNA vaccine rather than mRNA.
Some countries have tentatively paused vaccinations for some childhood age groups unless there are extenuating factors such as underlying disease, at-risk family members, etc.: Norway (for children < 15 years old) (Norwegian Institute of Public Health, 2022), Finland (for children < 12 years old) (Finnish Institute for Health and Welfare, 2022), Denmark (for children < 12 years old) (Danish Health Authority, 2022), and Sweden (for children < 12 years old) (Reuters, 2022).
Participants will be unblinded (U.S. FDA, 2022af) 6 months after their last dose thus ending any randomized and controlled evaluation of long-term risks.
It’s likely (U.S. FDA, 2022ab) that booster doses will be recommended thus increasing cumulative risks.
Bell’s palsy is a rare but known risk associated with mRNA vaccines (U.S. CDC, 2022f).
Guillain-Barré syndrome is a rare but known risk associated with mRNA vaccines (Hanson et al., 2022).
Potential risks of antibody-dependent enhancement (ADE), original antigenic sin, vaccine-acquired immunodeficiency syndrome, etc. (Yamamoto, 2022)
In children aged 5-11, between November 3 to February 27, 2022 (Hause et al., 2022), out of 7,578 reports of adverse events following vaccination submitted to the U.S. Vaccine Adverse Event Reporting System (VAERS), although only correlational (Rosenblum et al., 2022f), 194 were serious (2.6%), of which 4 were deaths (0.05%), and others included multisystem inflammatory syndrome in children (MIS-C), seizure, myocarditis, appendicitis, and allergic reaction. These numbers are out of about 16 million doses (Hause et al., 2022), although VAERS is subject to under-reporting and simulated reporting (Shimabukuro et al. 2015). Serious adverse events should be compared to normal background rates (Gubernot et al., 2021; Abara et al., 2022). Health impact reports were more common after the second dose (Hause et al., 2022b).
In children aged 12-17, between December 14, 2020 to July 16, 2021 (Hause et al., 2021), out of 9,246 reports of adverse events following vaccination submitted to the U.S. Vaccine Adverse Event Reporting System (VAERS), although only correlational (Rosenblum et al., 2022f), 860 were serious (9.3%), of which 14 were deaths (0.15%), and others included myocarditis. These numbers are out of about 8.7 million doses (Hause et al., 2021), although VAERS is subject to under-reporting and simulated reporting (Shimabukuro et al. 2015). Serious adverse events should be compared to normal background rates (Gubernot et al., 2021; Abara et al., 2022).
In adults, between December 2020 to June 2021 (Rosenblum et al., 2022b), out of 340,522 reports of adverse events following vaccination submitted to the U.S. Vaccine Adverse Event Reporting System (VAERS), although only correlational (Rosenblum et al., 2022f), 27,023 were serious (7.9%), of which 4,496 were deaths (1.3%), and others included COVID-19, coagulopathy, seizure, stroke, Bells’ palsy, anaphylaxis, myopericarditis, acute myocardial infarction, appendicitis, Guillain-Barré syndrome, multisystem inflammatory syndrome in adults, transverse myelitis, and narcolepsy. These numbers are out of about 298 million doses (Rosenblum et al., 2022c), although VAERS is subject to under-reporting and simulated reporting (Shimabukuro et al., 2015). Serious adverse events should be compared to normal background rates (Gubernot et al., 2021; Abara et al., 2022). Of the deaths with available death certificates, 46.5% were diseases of the heart (Rosenblum et al., 2022d). Health impact reports were more common after the second dose (Rosenblum et al., 2022e).
Post-marketing observational studies and disproportionality analyses may have various limitations (Fraiman et al., 2022b).