Immunogenicity similar across age groups; vaccine better tolerated in older versus younger adults
MONDAY, Nov. 23, 2020 (HealthDay News) — The novel chimpanzee adenovirus-vectored vaccine, ChAdOx1 nCoV-19, is well tolerated, especially among older adults, according to a study published online Nov. 18 in The Lancet.
Maheshi N. Ramasamy, D.Phil., from the University of Oxford in the United Kingdom, and colleagues describe the safety and immunogenicity of ChAdOx1 nCoV-19 among 562 healthy adults, including those aged 70 years and older; 552 participants were analyzable.
The researchers found that local and systemic reactions were more common among those who received ChAdOx1 nCoV-19 than those who received the control vaccine; reactions were similar to those reported previously but were less common in older adults (aged ≥56 years). Among those who received two standard doses of ChAdOx1 nCoV-19, local reactions were reported in 88, 73, and 61 percent of those aged 18 to 55, 56 to 69, and 70 years and older, respectively; systemic reactions were reported in 86, 77, and 65 percent, respectively. During the study period, 13 serious adverse events occurred, none of which were considered to be related to the study vaccine. Across the three age cohorts, participants who received two doses of vaccine had similar median antispike severe acute respiratory syndrome coronavirus 2 immunoglobulin G responses at 28 days after the boost dose. Neutralizing antibody titers were similar across age groups after a boost dose. More than 99 percent of 209 boosted participants had neutralizing antibodies by 14 days after the boost dose. At day 14 after a single standard dose of ChAdOx1 nCoV-19, T-cell responses peaked.
“Our new study answers some of these questions about protecting older adults, but questions remain about effectiveness and length of protection, and we need to confirm our results in older adults with underlying conditions to ensure that our vaccine protects those most at risk of severe COVID-19 disease,” a coauthor said in a statement.
Several authors disclosed financial ties to pharmaceutical companies, including AstraZeneca, which partially funded the study.
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