Primary vaccination

Results from two main clinical trials found that Nuvaxovid was effective at preventing COVID-19 in people from 12 years of age. In these studies, over 47,000 people were given two doses of Nuvaxovid or placebo (a dummy injection).

In the first study, conducted in adolescents and adults, around two thirds of participants received the vaccine and the others were given placebo.

The study, conducted in Mexico and the United States, found a 90.4% reduction in the number of symptomatic COVID-19 cases from 7 days after the second dose in adults who received Nuvaxovid (14 cases out of 17,312 people) compared with adults given placebo (63 out of 8,140 people). This means that the vaccine had a 90.4% efficacy in this study.

The trial also showed that the immune response to Nuvaxovid, which was measured as the level of antibodies against SARS-CoV-2, was comparable between adolescents and young adults aged 18 to 25 years. Compared with placebo, the vaccine led to an 80% reduction in the number of symptomatic COVID-19 cases seen from 7 days after the second dose onward in adolescents; six out of 1,205 adolescents who received the vaccine and 14 out of 594 who received placebo developed COVID-19.

The second study was carried out in the United Kingdom and included only adults. The study showed a similar reduction in the number of symptomatic COVID-19 cases in people who received Nuvaxovid (10 cases in 7,020 people) compared with people given placebo (96 in 7,019 people); in this study, the vaccine efficacy was 89.7%. Taken together, the results of the two studies show that Nuvaxovid was effective at preventing COVID-19 in both adults and adolescents. The original strain of SARS-CoV-2 and variants of concern such as Alpha, Beta and Delta were the most common viral strains circulating when the studies were ongoing. There is currently limited data on the efficacy of Nuvaxovid against other variants of concern, including Omicron.

Booster vaccination

Data from two studies showed a rise in antibody levels when a booster dose of Nuvaxovid was given in adults after primary vaccination with the vaccine. Data from an additional study also showed a rise in antibody levels when a booster dose of Nuvaxovid was given in adults after primary vaccination with an mRNA vaccine or adenoviral vector vaccine.