TUESDAY, Dec. 8, 2020 (HealthDay News) -- AstraZeneca's COVID-19 vaccine is safe and effective, new data from late-stage trials shows.
Overall, the vaccine protected against symptomatic disease in 70% of cases, according to a team led by researchers from Oxford University in England. Among study volunteers who got a half dose and then a full dose, the rate was 90%, while the rate was 62% in those given two full doses.
"Our findings indicate that our vaccine's efficacy exceeds the thresholds set by health authorities and may have a potential public health impact," said Oxford's Andrew Pollard, the lead author on the study.
The interim findings are from phase 3 trials in the United Kingdom and Brazil that included more than 11,600 participants. Most of them (82%) were between the ages of 18 and 55, because older people were recruited later and will be studied in future analyses of the data.
Safety data from nearly 24,000 people in four trials in the United Kingdom, Brazil and South Africa found that, over a median of 3.4 months, only three participants had serious side effects possibly related to the vaccine. All recovered or are recovering and remain in the trial, according to the findings published online Dec. 8 in The Lancet.
"The results presented in this report provide the key findings from our first interim analysis," study author Merryn Voysey, also from the University of Oxford, said in a journal news release. "In future analyses, with more data included as it becomes available, we will investigate differences in key subgroups such as older adults, various ethnicities, doses, timing of booster vaccines, and we will determine which immune responses equate to protection from infection or disease."
Previous clinical trials of the vaccine had found that the vaccine triggers antibody and T-cell immune responses, and is safe in people aged 18 and older.
The researchers haven't yet been able to assess how long the vaccine provides protection. More data needs to be collected to determine the length of time the vaccine is effective and the possible need for booster shots.
Study co-author Sarah Gilbert, also from Oxford, said, "Despite global spread of COVID-19, a large proportion of the population in many countries have not been infected and are not immune. Vaccines may play an important role in increasing immunity, preventing severe disease and reducing the health crisis, so the possibility that more than one efficacious vaccine may be approved for use in the near future is encouraging."
Gilbert added, "Here we have shown for the first time that an adenoviral vectored vaccine -- a type of vaccine technology which has been in use since 2009 -- is efficacious and could contribute to disease control in the COVID-19 pandemic."
Two other leading coronavirus vaccines, from Pfizer and Moderna, have shown roughly 95% effectiveness after two doses in late-stage trials. Both employ a newer technology that uses messenger RNA to prime the immune system to attack the new coronavirus. New data posted Tuesday on the U.S. Food and Drug Administration's website in advance of a Dec. 10 meeting of its vaccine advisory panel showed the Pfizer vaccine is 52% effective after one dose.
The U.S. Centers for Disease Control and Prevention has more on COVID-19 vaccination.
SOURCE: The Lancet, news release, Dec. 8, 2020