Post by Admin on Apr 6, 2021 21:05:46 GMT
VACCINE EFFICACY
Table 2.
Vaccine Efficacy against Mild-to-Moderate Symptomatic Covid-19 Confirmed by Nucleic Acid Amplification Test.
Figure 3.
Kaplan–Meyer Plot of ChAdOx1 nCoV-19 Vaccine Efficacy against Symptomatic Covid-19 Illness of Mild or Moderate Severity after Two Doses, as Compared with Placebo.
All 42 cases of Covid-19 were graded as mild (15 vaccine recipients and 17 placebo recipients) or moderate (4 vaccine recipients and 6 placebo recipients); there were no cases of severe disease or hospitalization in either group. The incidence of confirmed mild-to-moderate Covid-19 more than 14 days after the second dose among previously seronegative participants was 93.6 per 1000 person-years in the placebo group and 73.1 per 1000 person-years in the vaccine group; vaccine efficacy was 21.9% (95% CI, −49.9 to 59.8) (Table 2 and Figure 3). Similarly, among seropositive participants who had had a nonreactive nucleic acid amplification test before or at randomization, the incidence of mild-to-moderate Covid-19 more than 14 days after the second injection did not differ between placebo (81.9 per 1000 person-years) and vaccine (73.2 per 1000 person-years) recipients; vaccine efficacy was 10.6% (95% CI, −66.4 to 52.2) (Table S6).
Forty-one of the 42 nasal swab samples (97.6%) were successfully sequenced and classified; 39 (95.1%) cases were caused by the B.1.351 variant and 2 (4.9%; both in the placebo group) by the B.1.1.1 and B.1.144 lineages (Fig. S8). Further details of phylogenetic characterization are provided in the Supplementary Appendix. In a secondary-outcome analysis, efficacy against B.1.351 was not evident (vaccine efficacy, 10.4%; 95% CI, −76.8 to 54.8) (Table 2).
Results of analyses of other secondary and exploratory efficacy end points are detailed in Table S6. Overall vaccine efficacy for Covid-19 of any degree of severity more than 14 days after the first dose was 33.5% (95% CI, −13.4 to 61.7). Also presented in Table S6 are efficacy estimates for any symptomatic illness or asymptomatic SARS-CoV-2 infection after the first and second injections; differences in efficacy estimates were nonsignificant and were similar to those for mild-to-moderate Covid-19 estimates.
In a post hoc analysis of vaccine efficacy at more than 14 days after a single injection through October 31, 2020, as a proxy for infection by a non–B.1.351 variant (Fig. S1),15,27 the overall attack rate of mild-to-moderate Covid-19 at least 14 days after the first injection was 1.3% in placebo recipients and 0.3% in vaccine recipients; vaccine efficacy was 75.4% (95% CI, 8.7 to 95.5) (Table S8). Similar efficacy estimates were observed in other post hoc analyses for end points occurring through October 31, 2020.
Table 2.
Vaccine Efficacy against Mild-to-Moderate Symptomatic Covid-19 Confirmed by Nucleic Acid Amplification Test.
Figure 3.
Kaplan–Meyer Plot of ChAdOx1 nCoV-19 Vaccine Efficacy against Symptomatic Covid-19 Illness of Mild or Moderate Severity after Two Doses, as Compared with Placebo.
All 42 cases of Covid-19 were graded as mild (15 vaccine recipients and 17 placebo recipients) or moderate (4 vaccine recipients and 6 placebo recipients); there were no cases of severe disease or hospitalization in either group. The incidence of confirmed mild-to-moderate Covid-19 more than 14 days after the second dose among previously seronegative participants was 93.6 per 1000 person-years in the placebo group and 73.1 per 1000 person-years in the vaccine group; vaccine efficacy was 21.9% (95% CI, −49.9 to 59.8) (Table 2 and Figure 3). Similarly, among seropositive participants who had had a nonreactive nucleic acid amplification test before or at randomization, the incidence of mild-to-moderate Covid-19 more than 14 days after the second injection did not differ between placebo (81.9 per 1000 person-years) and vaccine (73.2 per 1000 person-years) recipients; vaccine efficacy was 10.6% (95% CI, −66.4 to 52.2) (Table S6).
Forty-one of the 42 nasal swab samples (97.6%) were successfully sequenced and classified; 39 (95.1%) cases were caused by the B.1.351 variant and 2 (4.9%; both in the placebo group) by the B.1.1.1 and B.1.144 lineages (Fig. S8). Further details of phylogenetic characterization are provided in the Supplementary Appendix. In a secondary-outcome analysis, efficacy against B.1.351 was not evident (vaccine efficacy, 10.4%; 95% CI, −76.8 to 54.8) (Table 2).
Results of analyses of other secondary and exploratory efficacy end points are detailed in Table S6. Overall vaccine efficacy for Covid-19 of any degree of severity more than 14 days after the first dose was 33.5% (95% CI, −13.4 to 61.7). Also presented in Table S6 are efficacy estimates for any symptomatic illness or asymptomatic SARS-CoV-2 infection after the first and second injections; differences in efficacy estimates were nonsignificant and were similar to those for mild-to-moderate Covid-19 estimates.
In a post hoc analysis of vaccine efficacy at more than 14 days after a single injection through October 31, 2020, as a proxy for infection by a non–B.1.351 variant (Fig. S1),15,27 the overall attack rate of mild-to-moderate Covid-19 at least 14 days after the first injection was 1.3% in placebo recipients and 0.3% in vaccine recipients; vaccine efficacy was 75.4% (95% CI, 8.7 to 95.5) (Table S8). Similar efficacy estimates were observed in other post hoc analyses for end points occurring through October 31, 2020.