" 2020 has been a difficult year for all, but has seen 58 vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) be developed and in clinical trials,
1 with some vaccines reportedly having more than 90% efficacy against COVID-19 in clinical trials.
This remarkable achievement is much-needed good news as COVID-19 cases are currently at their highest daily levels globally
.2 New vaccine efficacy results are reported now in The Lancet :
investigators of four randomised, controlled trials conducted in the UK, South Africa, and Brazil report pooled results of an interim analysis of safety and efficacy against COVID-19 of the Oxford–AstraZeneca chimpanzee adenovirus vectored vaccine ChAdOx1 nCoV-19 (AZD1222) in adults aged 18 years and older.
3 This is the first report of efficacy against COVID-19 for a non-profit vaccine aiming for global supply, equity, and commitment to low-income and middle-income countries (LMICs)
,4, 5 and as such its publication is very welcomed.
After phase 1 results supported a two-dose regimen, the trial protocols were amended where necessary to require two standard doses (SD/SD cohort) of approximately 5 × 1010 viral particles per dose administered 28 days apart, but a subset (LD/SD cohort) in one of the UK trials inadvertently received a half-dose of the vaccine (low dose) as the first dose before a change in dosage quantification methodology ; additionally, the protocol amendments enabled other trial participants originally scheduled to receive a single dose to receive a booster more than 28 days after their first dose.
Participants randomly received either the ChAdOx1 nCoV-19 vaccine or control, which was either meningococcal conjugate vaccine (MenACWY) or saline depending on the trial.
Interim efficacy results were available and are reported for two of the four ongoing trials (from the UK and Brazil) based on cases occurring within approximately 4 months of follow-up in 11 636 participants, the majority of whom were aged 18–55 years (10 218 [87·8%] participants), white (9625 [82·7%] participants), and female (7045 [60·5%] participants).
No COVID-19-related hospital admissions occurred in ChAdOx1 nCoV-19 recipients, whereas ten (two of which were severe) occurred in the control groups. Vaccine efficacy for the prespecified primary analysis (combining dose groups) against the primary endpoint of COVID-19 occurring more than 14 days after the second dose was 70·4% (95·8% CI 54·8 to 80·6 ; 30 [0·5%] of 5807 participants in the ChAdOx1 nCoV-19 group vs 101 [1·7%] of 5829 participants in the control group).
Surprisingly, however, efficacy was substantially lower in the SD/SD cohort (62·1% [95% CI 41·0 to 75·7] ; 27 [0·6%] of 4440 vs 71 [1·6%] of 4455) than in the LD/SD cohort (90·0% [67·4 to 97·0] ; three [0·2%] of 1367 vs 30 [2·2%] of 1374), which remained after accounting for differences in age and time between doses.
Efficacy was similar when evaluated starting at 21 days after the first standard dose (192 cases), suggesting there is at least short-term protection with one dose.
Although efficacy was lower (58·9% [1·0 to 82·9]) against asymptomatic infection in the LD/SD cohort (and unfortunately only 3·8% [−72·4 to 46·3] in the SD/SD group), the results nonetheless provide some hope that COVID-19 vaccines might be able to interrupt some asymptomatic transmission, although fewer data (69 cases among 6638 participants) were available with this outcome and more data are needed to confirm. Only 1418 (12·1%) of those assessed for efficacy were older than 55 years (none of whom were in the LD/SD cohort), meaning that from the interim analysis of these trials, we cannot yet infer efficacy in older adults, who are the group at greatest risk of severe COVID-19 outcomes.
Serious adverse events were evaluated in 12 174 ChAdOx1 nCoV-19 recipients and 11 879 control recipients.
No serious adverse events or deaths that were treatment associated occurred in ChAdOx1 nCoV-19 recipients.
There were 175 serious adverse events (84 in the ChAdOx1 nCoV-19 group and 91 in the control group), three of which were possibly related to the intervention : transverse myelitis occurring 14 days after a ChAdOx1 nCoV-19 booster vaccination, haemolytic anaemia in a control recipient, and fever higher than 40°C in a participant still masked to group allocation. Two additional transverse myelitis cases considered unlikely to be related to the intervention occurred : one 10 days after the first dose of ChAdOx1 nCoV-19 was attributed to pre-existing multiple sclerosis and one in a control group that occurred 68 days after vaccination.
The transverse myelitis cases resulted in temporarily pausing the trial and all participants have recovered or are recovering. ..
…. Despite the outstanding questions and challenges in delivering these vaccines, it is hard not to be excited about these findings and the existence of three safe and efficacious COVID-19 vaccines, with a further 55 already in clinical trials.1 With a range of manufacturers, a very large global investment in production, and cooperation in procurement and distribution, it seems likely that 2021 will see COVID-19 vaccines made available to all countries in the world—at least for their priority groups.
9 Perhaps by this time next year, we can celebrate the global control of SARS-CoV-2, in person.
MDK reports grants and personal fees from Merck and grants from Pfizer, outside of the area of work commented on here, and is a subgrant recipient on an unrelated study conducted by the principal investigator of this trial. CW has received grant funding and personal fees from Merck, outside of the area of work commented on here.