Childhood vaccinations provide immunity to children against serious infectious diseases before they are exposed to them to prevent illness. Many childhood diseases, such as smallpox and polio, have been almost completely eradicated as a result of widespread, standardized childhood vaccination programs. Some vaccinations, such as those for highly contagious diseases including measles, mumps, rubella, chickenpox, and diphtheria, are now commonly required for children to attend school, unless medically contraindicated. However, as the first COVID-19 vaccine has just been approved by the U.S. Food and Drug Administration for children under emergency use authorization, with others expected to follow soon, many are seeking information on the safety, efficacy, and necessity of COVID-19 vaccines for children, as parents face the critical decision of if and when to vaccinate. This blog answers the most common questions with an in-depth look at the available data and underlying science supporting the recent authorization of the Pfizer/BioNTech COVID-19 mRNA vaccine for children 12 and older.
On May 10th, the U.S. FDA granted an extension of the emergency use authorization for Pfizer/BioNTech’s COVID-19 vaccine for children ages 12-15 based on available safety and efficacy data. In their landmark phase 3 clinical trial that started in late July 2020, Pfizer/BioNTech enrolled 2,260 adolescents aged 12-15 without evidence of prior SARS-CoV-2 infection who received the COVID-19 BNT162b2 vaccine under the same two-shot protocol being used for adults. Among these participants, 1,131 were given the vaccine and 1,129 were given a placebo. There were zero infections in the vaccine group and 18 infections in the placebo group. These data showed the vaccine to have 100% efficacy in this age group, and serum antibody testing also showed a more robust antibody response in this age group than was seen in the 16-25 age group tested in previous trials. The adverse effects reported in this study did not differ from the effects that have been reported in other age groups and were generally mild. Thus, based on the available data, the Pfizer/BioNTech vaccine has proven to be very effective and safe for people 12 years and older. Pfizer/BioNTech has also committed to monitoring all children in the clinical trial for an additional two years to ensure there are no long-term consequences from the vaccine. Following the success of this trial, Pfizer/BioNTech also initiated a Phase 1 clinical trial with children 6 months to 12 years of age. Moderna is also conducting a clinical trial of their vaccine in children of similar age groups. All other COVID-19 vaccines are only approved for individuals 18 and over at this time.
As of April 29, 2021, the American Academy of Pediatrics has reported 3,782,724 COVID-19 cases in children in the U.S., with children representing 13.8% of all reported COVID-19 cases. Children comprised 1.2% - 3.1% of all hospitalizations, and the mortality rate in children with COVID-19 was 0.21%. This data supports that severe disease in children due to COVID-19 to date has been rare. However, a number of additional factors should be considered when assessing the necessity of vaccinating children against COVID-19.
The long-term physical effects of the virus on infected children are still unknown; however, potential long-term complications, such as multisystem inflammatory syndrome, have been documented in adults who were infected. Similar long-term effects have also been observed in children. In addition, the U.K. variant B.1.1.7 shows higher rates of infection in children, potentially increasing their risk in the future. The negative impact of the pandemic’s disruption on children’s mental health and education has also been well documented. In the end, necessity is relative. While most children’s risk of death or severe illness due to a COVID-19 infection is low based on available data to date, vaccination has been shown to protect them nearly completely against COVID-19 illness and any potential unknown long-term consequences. Vaccination also decreases the likelihood of children transmitting the disease to others at higher risk, may provide increased psychological safety that they and their loved ones are protected, and contributes to mitigation and hopefully eventual eradication of the disease in the overall population.
Children are not just miniature adults. Their immune system has some advantages when coping with novel pathogens. In the first months of life, babies are primarily protected from infectious diseases by the antibodies transferred to them from their mother. As these initial antibodies decay, children are often more susceptible to all kinds of microorganisms, because all of these are novel to their bodies. Thus, children’s immune systems are in a very active state as they continuously encounter novel pathogens. Since SARS-CoV-2 is a novel virus to both children and adults, it is very likely that children’s immune systems react more effectively to combat it.
Two significant components influence the increased robustness of children’s immune response to novel pathogens: the number of naïve T-cells and the location of those T-cells. Children have millions of naïve T-cell warriors, just waiting to be exposed to pathogens. This innate immune response to new pathogens is the first step in building immunity. In the second step, the body creates “memories”, in the form of memory immune cells that prepare it to respond to these pathogen invaders in the future. Children have a distinct advantage over adults in building immunity because as you age, your number of naive T-cells decreases. This also means that adults are slower to mount an immune response to a pathogen because they do not have as many T-cell warriors ready to react. The location of these naive T-cells also contributes to the more robust immune response to COVID-19 in children. A 2019 article in Nature Mucosal Immunology found that children have more naïve T-cells in specific tissues, not just in their blood. Another report in Nature noted that children also typically have increased exposure to other coronaviruses, like those that cause the common cold, contributing to a quicker immune response to SARS-CoV-2. For these reasons, children’s immune response to vaccinations and related side effects can differ significantly from those seen in adults. Thus, separate clinical trials in children are critical to prove safety and efficacy in this unique population and optimize appropriate dosing and clinical protocols.
Content Manager, CAS
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