The current study is a single-blind, randomised, controlled, phase 2/3 trial. The study population consisted of healthy adults aged 18 years and older. All study subjects were enrolled at two UK clinical research facilities, in an age-escalation manner as follows: 18–55 years, 56–69 years, and 70 years and older immunogenicity subgroups.
Participants were randomly assigned to receive intramuscular ChAdOx1 nCoV-19 [COVID related vaccine] or a control vaccine [MenACWY]. The schedule was to stratify subjects by age and dose group and study site, using the following ratios: in the 18–55 years group, 1:1 to either two doses of ChAdOx1 nCoV-19 or two doses of MenACWY; in the 56–69 years group, 3:1:3:1 to one dose of ChAdOx1 nCoV-19, one dose of MenACWY, two doses of ChAdOx1 nCoV-19, or two doses of MenACWY;
and in the 70 years and older, 5:1:5:1 to one dose of ChAdOx1 nCoV-19, one dose of MenACWY, two doses of ChAdOx1 nCoV-19, or two doses of MenACWY. Prime-booster regimens were given 28 days apart.
The specific objectives-outcomes of this part of the study were to evaluate safety and efficacy. The comparative results of the study were efficacy, as measured by the number of symptomatic and laboratory-confirmed COVID-19 cases and safety, as measured by the occurrence of serious adverse reactions.
Between May 30 and August 8, 2020, 560 participants enrolled in the study (160 between 18–55 years, 160 between 56–69 years, and 240 participants 70 years and older).
The following reactions were reported: local reactions, in 43 (88%) of the 49 participants in the 18–55 age group, 22 (73%) of the 30 in the 56–69 age group, and 30 (61%) of the 49 participants in the 70-year group and above. Systemic reactions [predominately fatigue, headache, feverishness, and myalgia ], in 42 (86%) participants in the 18–55 age group, 23 (77%) in the 56–69 age group and 32 (65%) in the 70 year group and over. 13 major adverse reactions occurred during the study period, none of which were considered to be related to the study vaccines.
In participants receiving two doses of vaccine, mean antibody titers (IgG versus coronavirus protein) 28 days after the first dose were similar in all three age groups. Neutralizing antibody titers after the second dose were similar in all age groups.
###Which is the main message from the above trial?
Considering previous data, vaccines are often less effective in the elderly. The current study is an example of how candidate vaccines seem to be effective for older people as well. We are looking forward to evaluate the results in terms of protection in phase 3 based studies. Furthermore the large sample could allow us to confirm the protection rate in all age groups.