According to a Phase 1b-2 trial published in the New England Journal of Medicine, the two-dose COVID-19 vaccine was developed by Oxford University / AstraZeneca Plc (NASDAQ: AZN) was ineffective against mild to moderate infections caused by mutated virus strain in South Africa, called the B.1.351 variant.
What happened: The study was led by scientists from the South African Medical Research Council for the research unit on vaccines and infectious diseases.
The trial evaluated the safety and efficacy of the AstraZeneca ChAdOx1 nCoV-19 vaccine in HIV-negative adults between 18 and 64 years of age. The median follow-up after the second dose was 121 days. Data show that the vaccine was generally 10.4% effective against the variant.
Of the 750 participants who received vaccine, 19 (2.5%) developed mild to moderate COVID-19 more than 14 days after the second dose, compared with 23 of 717 placebo recipients (3.2%).
The incidence of COVID-19 among the vaccine group was 731 per 1000 person-years, compared to 93.6 per 1000 person-years among the placebo group, for the efficacy of 21.9%.
Of the 42 total cases of COVID-19, 39 were caused by B1351 for the efficacy of the vaccine at this variant of 10.4%.
All 42 cases were moderate to moderate, and no patients were admitted to the hospital. The severe side effect rates were similar between the vaccine and placebo groups.
Only one serious vaccine-related event occurred, a fever of 40 ° C (104 ° F) after the first dose; the fever was eliminated within 24 hours, and no adverse events were seen after the second dose of the participant.
Why it matters: The study concluded by saying that although the development of second-generation COVID-19 vaccines against strains such as B1351 and P1 had begun, the only vaccines likely to be available for the remainder of 2021 were formulated against the original virus.
In early February, South African health officials discontinued the AstraZeneca-Oxford vaccine to investigate reports that it offers little protection against mild to moderate illness.
Instead, the country switched to using the Johnson & Johnson (NYSE: JNJ) vaccine to immunize health workers.
Price action: AZN shares fell 0.14% with the last check on Wednesday at $ 49.98 in market trading.
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