Inactivated Vaccine-Induced SARS-CoV-2 Variant-SpecificImmunity in Children
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2022
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Multiple vaccines against severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2) have been evaluated in clinical trials. However, trials addressing the immune
response in the pediatric population are scarce. The inactivated vaccine CoronaVac has
been shown to be safe and immunogenic in a phase 1/2 clinical trial in a pediatric cohort
in China. Here, we report interim safety and immunogenicity results of a phase 3 clinical
trial for CoronaVac in healthy children and adolescents in Chile. Participants 3 to 17 years
old received two doses of CoronaVac in a 4-week interval until 31 December 2021. Local
and systemic adverse reactions were registered for volunteers who received one or two
doses of CoronaVac. Whole-blood samples were collected from a subgroup of 148 participants
for humoral and cellular immunity analyses. The main adverse reaction reported after
the first and second doses was pain at the injection site. Four weeks after the second dose,
an increase in neutralizing antibody titer was observed in subjects relative to their baseline
visit. Similar results were found for activation of specific CD41 T cells. Neutralizing antibodies
were identified against the Delta and Omicron variants. However, these titers were lower
than those for the D614G strain. Importantly, comparable CD41 T cell responses were
detected against these variants of concern. Therefore, CoronaVac is safe and immunogenic
in subjects 3 to 17 years old, inducing neutralizing antibody secretion and activating CD41
T cells against SARS-CoV-2 and its variants. (This study has been registered at ClinicalTrials
.gov under no. NCT04992260.)