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Source: United Kingdom – Science Media Centre

Pfizer and BioNTech have announced that they have concluded phase 3 study of their COVID-19 vaccine candidate, demonstrating 95% efficacy.

Prof Stephen Evans, Professor of Pharmacoepidemiology, London School of Hygiene & Tropical Medicine, said:

“This announcement in a press release is very good news indeed. There are now rather more data accrued with, it is said, no serious side effects.

“The numbers of cases of confirmed (but mainly mild) cases of COVID-19 split on the vaccine to 162 on placebo. From the previous press release it could be calculated that the split when there were 94 cases was 8:86. This suggests that in the more recent data, all the extra 76 cases were in the placebo group. This is slightly surprising and a highly significant difference in the later data. We do not know the reason for this.

“The statistical lower bound on the efficacy is now about 90% with the current estimate of about 95%. There is still statistical uncertainty in these data and any suggestions that 95% is importantly different from 90% or 94% should be ignored.

“It seems there is some evidence that in older adults (but we do not have data in detail and there are probably no data for 80 years and older) there is also very good efficacy with minimal side effects. This is again very good news, not just for this vaccine, but as it also makes it more likely that other vaccines will also be reasonably effective in older adults.

“There is also good news that severe COVID-19 is reduced as well as mild disease. Again, there is considerable uncertainty because results are based on only ten cases, but this is nevertheless good evidence that the vaccine protects against severe disease. Differences between vaccines cannot be concluded on the basis of these results.

“While we await a full paper, the FDA will have access to much more data and details than in a published paper. The head of the Biologics Center at the FDA, responsible for vaccines, has assured us that no politically appointed people are present for the assessment of any vaccines – they are briefed but do not attend the relevant meetings.

“If the data are also submitted to the European Medicines Agency, then we can expect both agencies to conduct a very careful evaluation and we can rely on their conclusions. Relying on a press release is not enough.”


Prof Trudie Lang, Director, The Global Health Network, Nuffield Department of Medicine, University of Oxford, said:

“Today’s update from Pfizer provides further encouraging news and more detail on the protection against disease that their vaccine is showing from this definitive phase III trial. The detail on achieving 94% protection in the elderly participants in the trial is particularly excellent news.

“The company are reporting that they now have enough efficacy data to submit for approval from the regulatory authorities, who will undertake a detailed assessment of both the efficacy and safety data. We will need to wait and learn over time how long the protection lasts, and to see whether this vaccine can also prevent transmission – meanwhile, this vaccine does look likely to have a strong role immediately once it is approved in protecting health workers and the vulnerable from disease.

“Another encouraging detail from this update was that of those cases that were considered severe, 90% of these had been vaccinated with a placebo. This ability to mitigate severe disease was a key question and so it is impressive that over 90% efficacy appears to be being maintained across ages and severity of disease. The safety data also looks very reassuring.

“This is a remarkable and very reassuring situation that we find ourselves in. To go from identifying a new virus to having several vaccines at the point of applying for regulatory approval is an incredible milestone for science.

“Having worked on vaccine development in several diseases such as Malaria, TB and Ebola, I am really encouraged. The progress here, the faster ways of working and the new technologies developed can be taken forward into other vaccine programmes and benefit other diseases. The achievements here have been supported by strong global collaborations and taking forward lessons learnt previously from other vaccine development programmes. Now ensuring there is equitable distribution and implementation across the globe should be everyone’s focus, alongside working within and from communities everywhere to build trust in these vaccines.”

All our previous output on this subject can be seen at this weblink:

Declared interests

Prof Trudie Lang: “No conflicts of interest.”

None others received.

MIL OSI United Kingdom