As the US cautiously reopens, opinions remain divided whether these efforts are proceeding too rapidly for enhanced public safety or too slowly for sound economic expansion. Uniform in opinion however is the notion that an effective vaccine will diminish the noise of these other conversations. Previous optimistic projections had separate vaccines from the Pfizer and Oxford being available as early as fall of this year.
That is why this week's news reports that vaccine trials are encountering speed bumps have been especially disconcerting. In an interview with the Sunday Times, Professor Adrian Hill of Oxford told the Sunday Times that the vaccine would only have a "50%" chance of being successful. While he thought the vaccine was was constructed, Professor Hill was concerned that the prevalence of Covid-19 in the general population was decreasing so much that the vaccine might not show a benefit in decreasing the disease's rate of infection. Bizarrely, the vaccine would be shown as more effective if Covid-19 increased in the target population among the individuals not receiving the vaccine so that the presumed lower Covid-19 rate in those receiving the vaccine would be more impressive.
Professor Hill essentially relayed what is a concern of many investigators trying to show benefit in an intervention being studied: over performance in the placebo group in a study relative to a historical basis. Multiple reasons can cause this effect including in this case, a decreased disease rate. Other reasons include a change in behavior or therapy of the control group or an inaccurate understanding of the disease prevalence during trial design.
Independent of the reasons for this effect, the end result is the same: trial failure as the control group results and the intervention group result (in this case the vaccine group) will be nearly identical or statistically indistinguishable. A different study by the same group in macaques also revealed that while the vaccine seemed to prevent Covid-19 pneumonia, the macaques had viral loads in their upper respiratory tracts.
Issues with other vaccine groups also seemed to be surfacing. Pfizer essentially said that it was incapable of producing the manufacturing scale necessary to produce all the vaccines it was planning and would have to outsource a large proportion of the production. Immediately, thoughts of delayed rollouts loomed while other plants could be inspected and assured of proper vaccine safety and efficacy. Moderna's vaccine which produced neutralizing antibodies in 8 patients was met with skepticism that these antibodies were sufficient to prevent Covid-19 in larger studies.
Additionally, the concept emerged that all these efforts might result in decreases in Covid-19 disease but not transmission. If the latter occurred, then social distancing and quarantines would still be necessary to prevent massive disease surges.
Historically, vaccines took years and even decades for development as many of these issues regarding transmission prevention, disease reduction, and vaccine safety were being ironed out. Decreasing this time frame to 9-18 months as is hoped in this Covid-19 pandemic would be spectacular and a testament to the incredible advances in modern science.
Or it could be hoping for too much.
https://www.telegraph.co.uk/news/2020/05/23/oxford-university-covid-19-vaccine-trial-has-50-per-cent-chance/