BACKGROUND AND PURPOSE:

• Ad26.COV2.S, known as the Johnson & Johnson COVID-19 vaccine in the US, is a viral vector vaccine that uses an adenovirus vector encoding SARS-CoV-2 spike protein
• Sadoff et al. (NEJM, 2021) report the primary analyses of an ongoing phase 3 trial to evaluate the safety and efficacy of a single dose for prevention of COVID-19 and SARS-CoV-2 infection in adults

METHODS:

• International, randomized, double-blind, placebo-controlled, phase 3 trial
• Participants
  • Adults aged 18 to 59 years of age
  • Seronegative or unknown serostatus at the start of the study (‘per protocol’ patients)
• Intervention
  • Single dose
  • Placebo
• Primary outcomes
  • Vaccine efficacy against moderate to severe/critical COVID-19
    • Onset at least 14 days after vaccination
    • Onset at least 28 days after vaccination
  • Safety

RESULTS:

• 19,630 received vaccine | 19,691 received placebo
• Vaccine protected against moderate to severe/critical Covid-19
  • Cases with onset at least 14 days after administration
    • Vaccine group: 116 cases
    • Placebo group: 348 cases
    • Efficacy 66.9% (adjusted 95% CI, 59.0 to 73.4)
  • Cases with onset at least 28 days after administration
    • Vaccine group: 66 cases
    • Placebo group: 193 cases
    • Efficacy 66.1% (adjusted 95% CI, 55.0 to 74.8)
• Vaccine efficacy was higher against severe–critical Covid-19
  • Severe cases with onset at least 14 days after administration
    • Efficacy 76.7% (adjusted 95% CI, 54.6 to 89.1)
  • Severe cases with onset at least 28 days after administration
    • Efficacy 85.4% (adjusted 95% CI, 54.2 to 96.9)

Efficacy Against South Africa Variant (B.1.351)

• Vaccine efficacy was maintained against South Africa variant against moderate to severe/critical COVID-19
  • Moderate to severe–critical efficacy
    • Onset at least 14 days after administration: 52.0%
    • Onset at least 28 days after administration: 64.0%
  • Severe-critical efficacy
    • Onset at least 14 days after administration: 73.1%
    • Onset at least 28 days after administration: 81.7%
• Vaccine safety
  • Reactogenicity was higher with than with placebo but was generally mild to moderate and transient
  • Incidence of serious adverse events did not differ between groups
• Deaths
  • Vaccine group: 3 deaths (none related to COVID-19)
  • Placebo group: 16 deaths (5 COVID-19 related)

CONCLUSION:

• The J&J vaccine was effective at preventing  COVID-19 at least 28 days after vaccination, especially against severe/critical COVID-19
• Efficacy was still high in South Africa, where a majority of COVID-19 cases were due to the South African variant
• There were no major adverse events associated with vaccination
• There were no COVID-19 related deaths in the vaccine group

Learn More – Primary Sources:

Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against Covid-19