The representation of pediatric participants in the study population for the Pfizer-BioNTech Covid 19 vaccine is too limited to adequately evaluate efficacy in pediatric age groups younger than 16 years.
As per data presented before the US FDA which approved the vaccine, the proceedings also looked at the unknown benefits and data gaps as per the FDA briefing document.
Pfizer has told the US FDA that its plans for the vaccine clinical studies include boostability, dose ranging and studies in pediatrics, use in pregnancy, use in immunocompromised, refrigerator stable second-generation formulation and co-administration of influenza vaccine being considered.
On the duration of protection, as the interim and final analyses have a limited length of follow-up, it is not possible to assess sustained efficacy over a period longer than 2 months.
On the effectiveness in pediatric populations, the representation of pediatric participants in the study population is too limited to adequately evaluate efficacy in pediatric age groups younger than 16 years.
No efficacy data are available from participants ages 15 years and younger. Although adolescents 16 to 17 years of age were included in the overall efficacy analysis, only one confirmed COVID-19 case was reported in this age group.
“However, it is biologically reasonable to extrapolate that effectiveness in ages 16 to 17 years would be similar to effectiveness in younger adults,” as per the FDA briefing document. Efficacy surveillance continued beyond November 14, 2020, and Pfizer has represented that additional data will be provided.
On the vaccine effectiveness against asymptomatic infection, data are limited to assess the effect of the vaccine against asymptomatic infection as measured by detection of the virus and/or detection of antibodies against non-vaccine antigens that would indicate infection rather than an immune response induced by the vaccine.
Additional evaluations will be needed to assess the effect of the vaccine in preventing asymptomatic infection, including data from clinical trials and from the vaccine’s use post-authorization.
Vaccine effectiveness against long-term effects of COVID-19 disease COVID-19 disease may have long-term effects on certain organs, and at present it is not possible to assess whether the vaccine will have an impact on specific long-term sequelae of COVID-19 disease in individuals who are infected despite vaccination.
Demonstrated high efficacy against symptomatic COVID-19 should translate to overall prevention of COVID-19- related sequelae in vaccinated populations, though it is possible that asymptomatic infections may not be prevented as effectively as symptomatic infections and may be associated with sequelae that are either late-onset or undetected at the time of infection (e.g., myocarditis). Additional evaluations will be needed to assess the effect of the vaccine in preventing long-term effects of COVID-19, including data from clinical trials and from the vaccine’s use postauthorization, the review said.
On the effectiveness in individuals previously infected with SARS-CoV-2, the primary endpoint was evaluated in individuals without prior evidence of COVID-19 disease, and very few cases of confirmed COVID-19 occurred among participants with evidence of infection prior to vaccination (although more cases occurred in the placebo group compared with the vaccine group).
“Therefore, available data are insufficient to make conclusions about benefit in individuals with prior SARS-CoV-2 infection. However, available data, while limited, do suggest that previously infected individuals can be at risk of COVID-19 (i.e., reinfection) and could benefit from vaccination”, the review said.
On the vaccine effectiveness against mortality, the review said a larger number of individuals at high risk of COVID-19 and higher attack rates would be needed to confirm efficacy of the vaccine against mortality. However, non-COVID vaccines (e.g., influenza) that are efficacious against disease have also been shown to prevent disease associated death. Benefits in preventing death should be evaluated in large observational studies following authorization, it said.
Pfizer while seeking EUA for the vaccine told the US FDA that the vaccine is effective for the prevention of Coronavirus Disease 2019 (COVID-19) caused by SARS-CoV-2 in individuals 16 years of age and older, no safety concerns identified in 43,448 subjects analyzed, no evidence of enhanced disease in vaccine recipients. The observed overall efficacy was 95 per cent, efficacious in younger and older adults, efficacious across diverse demographics and at-risk individuals and efficacious against severe disease.
Pfizer said there is similar efficacy for key high-risk subgroups including the elderly and racial/ethnic minorities, reactogenicity profile and SAEs comparable to other licensed vaccines and extensive post-approval pharmacovigilance in place.
Pfizer said timing is important to impact the pandemic as 55,000 US deaths per month could occur over the next few months and a Covid 19 vaccine can prevent many deaths. A pandemic vaccine must be introduced before the peak of cases to have maximal impact. A highly effective vaccine may be able to induce herd immunity, Pfizer said.
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