Nationwide Study on Pfizer COVID-19 Vaccine Effectiveness for Ages 12 to 18 – “The Vaccine Works for Children!”

A team of researchers at the MUSC Shawn Jenkins Children’s Hospital contributed to a nationwide study on the effectiveness of Pfizer-BioNTech’s COVID-19 vaccine against hospitalization in children age 12-18. The study was conducted by 19 hospitals in 16 states. The results of the study, published in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, show that the vaccine is effective against hospitalization in that population.

“People assume that children have a much milder COVID-19 course. But the Delta variant is different,” said Elizabeth Mack, M.D., pediatric critical care physician and principal investigator for the MUSC study site.

Mack explained that 100% of COVID-19 pediatric patients hospitalized at the MUSC Shawn Jenkins Children’s Hospital since the beginning of the pandemic have been unvaccinated.

Mack also emphasized that children infected with the Delta variant were more likely to have disease similar to the adult phenotype. In other words, all of their organs are at risk of damage, not exclusively the lungs. Children in the South were at an especially high risk due to low vaccination rates and a high number of comorbidities, including obesity and asthma.

“We have seen children with COVID-19 in the ICU with horrendous respiratory failure, kidney failure, liver failure, cardiovascular failure, and we’ve unfortunately seen deaths as well,” said Mack.

The nationwide study included 464 hospitalized children age 12-18. Some of these children were hospitalized for COVID-19. Other children in the study were enrolled as controls hospitalized with syndromes similar to COVID-19, like pneumonia, or with syndromes unrelated to COVID-19, like a broken leg. Vaccination and exposure history were then studied for COVID-19 patients and control patients. The MUSC Shawn Jenkins Children’s Hospital continues to add hospitalized COVID-19 patients to the study.

“The point of this study was to look at the Pfizer-BioNTech vaccine effectiveness in children in the 12- to 18-year-old age group after receiving two shots,” said Mack. “The results showed that the vaccine was extremely effective, and that some of the hospitalized COVID-19 patients who were not protected with the vaccine had some pretty severe courses.”

Mack also explained that there was a high frequency of cardiac muscle inflammation due to either COVID-19 or multisystem inflammatory syndrome in children, distinct from the very low risk of myocarditis related to the vaccine.

“We only had one or two cases of cardiac muscle inflammation due to the vaccine, and those patients had normal cardiac function and required only ibuprofen. They were discharged home in a day or two,” explained Mack.

In South Carolina, 66% of children age 12-19 are still unvaccinated.

“The low vaccination rates in the pediatric population at this point are not likely primarily related to vaccine access,” said Mack, as she explained some parents are hesitant to get their children vaccinated. “Fertility and puberty are the top concerns parents have, but thankfully the data supports vaccination of adolescents and women without negative impact on these issues.”

Mack explained that studies looking at the long-term effects of the vaccine are ongoing. However, the long-term effects of COVID-19 have already been devastating. Some children have needed intense inpatient rehabilitation, others have required tracheostomy placement, and still others have had lasting kidney or cardiac disease. 

“In the ICU, we see a lot of parents wishing their children were vaccinated,” said Mack. “Those children have multisystem organ failures, months in the ICU, lots of procedures, financial devastation and loss of school time.”

The study showed that the Pfizer-BioNtech vaccine was effective against hospitalization in patients age 12-18, during the period when the Delta variant was predominant.

“COVID-19 and its effects are all ‘vaccine-preventable,’” emphasized Mack. “The vaccine works for children!”

Reference: “Effectiveness of Pfizer-BioNTech mRNA Vaccination Against COVID-19 Hospitalization Among Persons Aged 12–18 Years — United States, June–September 2021” by Samantha M. Olson, MPH; Margaret M. Newhams, MPH; Natasha B. Halasa, MD; Ashley M. Price, MPH; Julie A. Boom, MD; Leila C. Sahni, PhD; Katherine Irby, MD; Tracie C. Walker, MD; Stephanie P. Schwartz, MD; Pia S. Pannaraj, MD; Aline B. Maddux, MD; Tamara T. Bradford, MD; Ryan A. Nofziger, MD; Benjamin J. Boutselis; Melissa L. Cullimore, MD; Elizabeth H. Mack, MD; Jennifer E. Schuster, MD; Shira J. Gertz, MD; Natalie Z. Cvijanovich, MD; Michele Kong, MD; Melissa A. Cameron, MD; Mary A. Staat, MD; Emily R. Levy, MD; Brandon M. Chatani, MD; Kathleen Chiotos, MD; Laura D. Zambrano, PhD; Angela P. Campbell, MD; Manish M. Patel, MD; Adrienne G. Randolph, MD and Overcoming COVID-19 Investigators, 19 October 2021, Morbidity and Mortality Weekly Repor.
DOI: 10.15585/mmwr.mm7042e1