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Vaccine effectiveness in preventing hospitalization in people ages 12-18 is 93%, according to a newly released report from a collaborative of 19 pediatric hospitals in 16 US states that assessed the initial 2-dose series of the Pfizer-BioNTech Covid-19 vaccine. The study was published in the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report. The analysis is the first of its kind large enough to pinpoint a precise figure during the Delta era. The protection was similar among patients ages 12-15 compared to those ages 16-18.
One reason many teens have yet to receive a Covid-19 vaccination is the belief that Covid-19 does not cause harm to younger people. This myth has been perpetuated by unwise comparisons between age groups. Yes, older people are far more likely to be hospitalized with Covid-19 than adolescents. But the Covid-19 threat in young people can no longer be discounted, as over 70,000 US residents under age 18 have been hospitalized, and thousands more have suffered medium-term serious complications. Over 700 US residents under age 18 have died from Covid-19.
Previous studies have not been large enough to measure whether Covid-19 vaccinations prevented hospitalization in persons ages 12-18, especially during the Delta era (protection against all Covid-19 disease during the pre-Delta era was extremely high). The new information reflects “real world data,” meaning that researchers tracked what happened in hospitals after the vaccines were authorized for use. Every time a patient with Covid-19 was hospitalized, researchers determined their vaccination status. Also, every time such a patient was hospitalized, researchers matched that case with two “control” patients, one hospitalized patient with Covid-like symptoms but who tested negative for the virus (i.e. they were hospitalized for some other reason but also had respiratory symptoms) and one hospitalized patient without Covid-like symptoms. In this way, the investigators could track various outcomes and have a reasonable group of patients for comparison.
Among children ages 12-18 who were hospitalized with Covid-19, 97% were unvaccinated. None of the vaccinated children required intensive care. None of the vaccinated children had to be placed in a coma so that they could live on mechanical ventilation (i.e. breathing machines). None of the vaccinated children required “lung bypass” machines (called extracorporeal membrane oxygenation, or ECMO). None of the vaccinated children required medications to support their blood pressure. None of the vaccinated children died.
Among the unvaccinated children hospitalized with Covid-19, 44% required intensive care, and 17% required life support (breathing machines, ECMO, blood pressure support). Two patients died.
In addition to these outcomes, the average length of hospitalization among breakthrough cases (6 of the 179 Covid-19 hospitalizations) was 3 days versus 5 days among the unvaccinated. Cases requiring intensive care were obviously much longer, meaning that some unvaccinated patients likely spent weeks in the hospital.
While the network of hospitals that participated in the study included major pediatric hospitals from the 4 US Census regions (Northeast, Midwest, South, and West), 61% of the Covid-19 hospitalizations occurred in the South, even though just 36% of the nation’s population ages 12-18 lives in the South. Unsurprisingly, vaccination rates in the South have trailed other regions.
In addition, patients hospitalized with Covid-19 were more likely to live in subregions with higher scores on the “social vulnerability index,” a metric which measures whether a community is at risk of experiencing the worst effects of a crisis, be it a hurricane or an infectious disease outbreak. Black and Hispanic (any race) patients accounted for around 52% of the hospitalizations, though these groups account for 46% of the teen population nationwide.
The way that the study was designed also adds important evidence against a pervasive narrative that Covid-19-related hospitalizations in children are merely “incidental” (i.e. that the children were hospitalized for other reasons and happened to have SARS-CoV-2 at the time of admission). Any attempt to debunk the findings of this study based on that argument won’t succeed because only patients with Covid-19 symptoms were included in the analysis.
Pre-existing conditions were common among the children hospitalized. But many of these conditions were “not extreme,” and included common conditions such as asthma (24%). A variety of other conditions were present among the Covid-19 patients, but their severity can’t be determined. For example, around 12% of the those hospitalized had some variety of neurologic or neuromuscular disorder. Did these teens have mild cases of attention deficit disorder, or far more serious conditions? Similarly, around 12% of the patients had diabetes, but we can’t say how serious these cases were.
What we can say is that most of these hospitalizations were not driven by two of the most dangerous conditions we think about when assessing severe Covid-19 risk: cancer and other immune system suppressing medical disorders. Among the patients hospitalized for Covid-19, a history of cancer (active or prior) or an immune-suppressing condition was present in just 4.5% of the cases. While it is hard to know the overall risk profile of the children included in this study, 68% of them were attending in-person school at the time of their hospitalization.
Lastly, among the 3% of the hospitalizations that occurred in fully vaccinated patients, on average, 55 days had elapsed between the time of the 2nd vaccination and the onset of Covid-19 symptoms. This implies, albeit indirectly, that the illnesses were not a result of waning immunity. Rather, we must acknowledge that the vaccines are excellent but imperfect. There is something we can do to increase the benefit of vaccinations: increasing the rates of vaccination. At the time this study was published, just 46% of the US population ages 12-15 had been vaccinated, and 54% of the population ages 16-17. Increasing vaccination rates will lower community spread. That’s our fastest path to normalcy.
Does knowing that vaccination prevents Covid-19 hospitalization in teens change how you feel about their use in this age group? Please add your comments and questions below.