I don't see an issue as particpants are randomly and blindly allocated to vaccine v placebo. It shouldn't change the ratio-
Unless the vaccine protects less well against asymptomatic disease which I cant see is inherently likely.
The difference is that as they're not actively testing the volunteers - then the rate of CV infection is likely to be between 4 to 6x (or more) higher. So if more people are getting infected then the efficacy (protecting people from getting infected) is 1/4 to 1/6th of 95% so say between 16 to 25%.
The maths can be confusing here. The important unspoken link is that while there may be 40,000 volunteers - just like in the broader community - not everyone is catching CV.
So the analysis (that is yet to be done or verified) then looks at if the 40,000 are a representative sample of the entire population then after 3 months as the entire population who have tested positive is 0.3% we would expect 120 people would have caught the virus.
However - those 120 could be say 20 symptomatic & 100 asymptomatic.
So reporting that 'observed' symptomatic are X does not tell anywhere near the full story. For example, perhaps the vaccine lessens the impact of CV but you can still catch it & spread it as you are asympomatic. Thats why these trials normally take much much longer to come to the ultimate result.
However, due to the severity of CV etc etc, certain protocols are being waved through. For example? How long does the vaccine last for? Do people who were vaccinated develop any long term issues? With the speeding up - this part is being bypassed in the interests of getting it out.
Historically all previously created CV vaccines produced too many adverse long term side effects & were dropped as the risks far out-weighed the benefit. Luckily, so far the worst side-effect does not appear to have shown itself - making the patient more likely to die.
Hopefully none of them will but there have been too many 'wonder drugs' that went through the lengthy processes that turned out not so well. Thalidomyde for example.