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Covid 19 Vaccine For Kids Under 5

The Facts

On June 15th the VRBPAC unanimously decided to recommend both the Moderna vaccine for children from 6 months to under 5 and the Pfizer vaccine for children 6 months through 4 years for FDA approval. All of the voting participants expressed that they wanted parents and pediatricians to have the CHOICE to vaccinate this age group, but did not specify that all children SHOULD get vaccinated. The Moderna dose for children under five is two 25 microgram doses four weeks apart. The Pfizer dose for children 6 months to 5 is three, 3 micrograms doses three weeks apart. The Evidence Safety: The side effects were less pronounced in the Pfizer vaccine group. This makes sense because the dose was lower. The primary difference in side effects was the incidence of a fever 1:20 (Pfizer) v 1:4 (Moderna), injection site pain, and fatigue (remember these symptoms are actually good as they signal your immune system is working). These are the same types of symptoms the adult population experiences. There was no concerning adverse effects noted, however, the study population was too small to catch rare events. Thus, the absence of adverse events in the clinical trial does not mean there will not be safety concerns once more children receive the vaccine. I would have liked to see a larger trial and longer follow-up period in terms of establishing a robust safety profile in this age group. However, I think that the probability of a serious safety issue is low based on the current data. Efficacy: Two doses of the Pfizer vaccine had 0% efficacy--this is why the initial two dose VRBPAC meeting was delayed without reason. This finding surprised many, and is likely evidence that Pfizer under-dosed. However, when three doses were tested, they produced a result similar to that of adults who showed an initially robust antibody response. It is worth noting that efficacy was measured in terms of preventing infection NOT preventing severe disease. So even though the two doses produced 0% efficacy in terms of preventing infection that does not mean it did not help elicit a B or T cell response that would theoretically help prevent against long COVID and severe disease. The three Pfizer doses had “80%” efficacy, but only 3 cases went into concluding this value, meaning it is statistically VERY weak and the true percentage could have a large range. The confidence interval was 14% to 96%. This means we need to rely on immunobridging. Immunobridging is the process of estimating vaccine efficacy by comparing the number of neutralizing antibodies with those of a similar population and then seeing how many people in that other population actually got sick. Neutralizing antibodies are the closest proxy we have to establishing vaccine efficacy without case counts. The Bottom Line: Both vaccines worked (meaning they met the primary endpoints) but one more dose of Pfizer is needed to catch up to the efficacy of Moderna. Both vaccines appeared to be safe based on existing data. The time of protection conferred by these vaccines is probably similar to adults--lasting approximately 6 months for any infection protection, but working longer to protect against severe disease. I assume this based on the neutralizing antibody titres which were similar to the younger adult population. These studies had short-term safety follow-up (two months post the last dose), and even shorter term follow-up of measurement of the neutralizing antibodies and case counts (4 weeks post last dose). However, we have a wealth of evidence from other populations that makes these shorter study periods acceptable, and the data we did receive was encouraging. FAQ’s: What if my child already had COVID? Having COVID, particularly recently (within the last 4 months), will provide some protection, however, the best protection is a mixture of both vaccination and natural infection. We call this hybrid immunity. Studies show the vaccine can increase the antibodies from the hundreds (from natural infection) to the thousands (vaccination). How long will protection last? We don’t know. But, if you extrapolate data from the adult population, we see antibodies waning significantly at around 6 months post vaccination. However, severe disease protection lasts even longer, so far we have shown it can last to at least two years in healthy, younger populations. What if my child is immunocompromised? All the more reason to consider the vaccine, as it will help prevent against both severe disease (hospitalization) and long COVID. One of the most concerning risk factors for severe disease in children is obesity. Do healthy children need the vaccine? 50% of pediatric hospitalizations from COVID-19 occurred in previously healthy children with no underlying conditions. It is difficult to predict who is going to be seriously affected. Further, we vaccinate for childhood diseases that cause much less sickness, hospitalizations and deaths than COVID-19--a point the VRBPAC emphasized during the committee meeting this week. Hospitalizations among children for COVID-19 are still low, do I really need to vaccinate my child? Hospitalizations may be rare, but long covid is not. Long covid has been shown to have neurological, cardiac and respiratory implications, even showing lowered IQ scores in some studies. Vaccinated adults have been shown to have a significant reduction in long covid compared to those who were not vaccinated. It is reasonable to assume that vaccinating your children will reduce the probability they will develop long covid if infected. Are you going to vaccinate your children, and if so which vaccine are you choosing? I have a 3 year old and a 1 year old. To date, neither of them have had COVID-19. Because of that, they are particularly vulnerable. I am leaning towards vaccinating with Moderna because Pfizer is only effective after 3 doses, and that efficacy has not been strongly established yet. Moderna is effective after 2 doses, and I believe because of the higher dose, the protection will last for longer. Further, the safety profiles are similar between the two vaccines and Moderna had more trial participants (and therefore more data). Additionally, my children have not shown any serious reactions to other vaccines, nor any allergies. In sum, the totality of the evidence leads me to believe that for my kids the benefits of the Moderna vaccine outweighs any benefits of the lower dose Pfizer vaccine. The choice to vaccinate young children is not as straightforward as it has been in the other age groups. Hospitalizations in children with COVID-19 is rare, but not as rare as it is with other diseases we vaccinate against. Many of these hospitalizations (and deaths) are also PREVENTABLE. Although the issue is complex, it is difficult, based on the current data, to argue against vaccination in this age group.

Stay Safe and Healthy, Dr. Jen Dunphy

**I am not a medical doctor, but a doctor of public health (DrPH) and I am not giving any clinical advice. My job is to help interpret leading research and make sense of the probable implications. Please consult your physician for any medical advice. Thank you.

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