COVID-19(17) SARS-CoV-2(11) children(7) vaccination(7) pediatric(6) Vaccine(6) Critical(5) COVID-19 pandemic(5) Population(4) Administered(4) reduced(4) COVID-19 vaccine(4) clinical trials(4) distribution(4) Vaccine-induced immunity(4) shown(4) pandemic(4) Vaccines.(4) dose(4) country(4) observational studies(4) Other(4) effort(4) approved(4) variant(4) COVID-19 vaccines(4) strain(4) effective(4) risk(4) clinical trial(4)