Evidence for vaccine protection.
Good news for science and humanity.
11th November 2020:
Since the start of the Covid-19 pandemic, scientists have been working on a vaccine, an intervention thought by many to be the most important means for bringing the infection under control. Few can argue with this as we currently anguish over 50 million cases of infection, 1.26 million deaths and a severe slowdown on global economic activity. It has resulted in the worst recession in 300 years, affected lives and livelihoods (double jeopardy) – one in 10 unemployed. Economic inequality has widened, is getting worse and disproportionately affects those already deprived and vulnerable.
On November 9th a press release reported encouraging preliminary results from efficacy trials of a Covid-19 vaccine developed by a German company (BioNTech) and the US pharmaceutical company Pfizer. The headline is that the vaccine, tested in more than 40,000 volunteers, prevented Covid-19 infection in more than 90% of those immunised. It is an interim analysis meaning that the trial is not finished, but the code was broken after 64 Covid-19 infections had been documented; 59 of these occurred in the volunteers who did not receive 2 doses of vaccine given about 4 weeks apart. Although details from a peer-reviewed scientific article will not be published for several weeks or longer, these results do suggest a breakthrough. For the first time we have evidence that immune responses to the spike protein of Covid-19 are protective. Almost all other vaccines currently being developed are based on this rationale. This is a huge step forward but of course these results need to be interpreted with the caution merited by the limited amount of information that is available. Given such relatively small numbers, we need much more data on the safety of the vaccine.
Aside from safety data, other key issues include:
- does the vaccine affect transmission within populations (indirect, community or ‘herd’ protection), or only the person who is immunised?
- how long does the protection last?
- how do variables such as age, gender, ethnicity, economic status. geography, climate, prior health status (co-morbidities) affect the outcome of immunisation?
- will further booster doses be needed?
To consider the first of these bullet points, the strategies for rolling out immunisation would be very different depending on whether the vaccine, in addition to protecting the immunised individual, also interrupts transmission of the virus. The reality is that we will not have answers to this key question for a long time because the current trials (this also applies to other vaccines in development) do not evaluate the impact of the vaccine on the community (herd immunity). Therefore, when the roll-out of the vaccine occurs, the approach will be based on protection of the most vulnerable, front-line workers etc. If later evidence indicates that the vaccine stops spread of the virus, then the strategy might preferentially target those who spread the disease, even if these “spreaders” are themselves not prone to get severe disease.
One of the most exciting aspects of today’s news is that within less than a year, scientists have made significant progress in developing an effective vaccine. This was not a given and for many important microbes, progress on developing vaccines has stalled. For example, despite 40 years of relentless and hugely costly investment, there have been no breakthroughs in research and development of vaccines to prevent the Human Immunodeficiency Virus (HIV).
It is extremely important too that the Pfizer-BioNTech vaccine provides proof of concept of a new vaccine technology using RNA (see textbox below).
The results from Pfizer-BioNTech offer encouragement to others who are using this or similar methods to induce immunity via the Covid-19 Spike protein. Indeed, breaking news today (November 11th) indicates that Russian scientists have obtained similar levels of protection for their Sputnik V vaccine. After 20 confirmed cases, 18 Covid-19 infections occurred in those who did not receive the vaccine, an estimated efficacy of 92%, similar to that of the Pfizer-BioNTech vaccine, although in a trial of fewer persons. In the coming weeks, it is certain that the results of more trials, including the Oxford-AstraZeneca vaccine, will be announced.
This makes for optimism that we may have a spring in our step by summer as we face further weeks of restrictions and the prospect of a not-so-merry Christmas.
Copyright Richard Moxon 11.11.20
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