Four week ago, Pfizer Inc., the US-based multinational pharmaceutical corporation was betting that its coronavirus vaccine candidate will show clear evidence of effectiveness early in its clinical trial. It was according to the company and internal documents reviewed by Reuters that describe how the trial was being run. That time, the organization also stated that it would be clear by the end of October whether the vaccine, developed together with Germany’s BioNTech SE, is safe and effective. Now, the time has come. Side effects that have emerged in a large late-stage trial of a Covid-19 vaccine candidate from Pfizer Inc. and BioNTech SE are in line with those seen in smaller early studies, a positive sign for one of the front-runners in the race for a shot. Ugur Sahin, Chief Executive Officer, BioNTech said in an interview that the partners haven’t had to stop their late-stage study over safety concerns. They’re sticking with their previously announced target of being able to show as soon as this month whether the vaccine works. That would put Pfizer and BioNTech on track to potentially be the first to show the efficacy of a Covid-19 vaccine, in an environment of intense scrutiny over every possible complication.

This week, Eli Lilly & Co. and Johnson & Johnson both said they had to pause research on potential therapies or shots because of safety concerns. Meanwhile, U.S. President Donald Trump has touted unproven treatments and pushed for more rapid regulatory review. The pauses in other studies show “there is no room for ignoring facts,” stated Ugur Sahin. “If there is a concern, the process stops. No one closes their eyes, and it should give people confidence that if a vaccine survives the development process and is approved, it should be regarded as safe.”

Pfizer and BioNTech chose their candidate from a slate of four contenders, all of which relied on messenger RNA technology designed to teach the body’s cells to become vaccine factories in their own right. In what Ugur Sahin said is an unusual step, Pfizer and BioNTech published some of the data they used to narrow the field in the New England Journal of Medicine on Wednesday.

The results show that people who took the experimental shot they chose had fewer so-called systemic side effects, things like fever, chills and fatigue, than those who got another jab in the partners’ portfolio. Because of the structure of the trial, BioNTech and Pfizer had first disclosed early results for another vaccine candidate, BNT162b1, in July.

Investors were already optimistic about prospects for BNT162b1, but after comparing data the companies decided instead to pursue another candidate, BNT162b2. That one performed as well in elderly people in the study as it did in young participants, said Ugur Sahin, an important consideration for a coronavirus vaccine. Similar Effects With just 195 participants, the early study was too small to show the real safety implications of the experimental shot. Still, the side effects that have emerged so far in the 44,000-person late-stage trial are similar to those seen in these early studies, stated Ugur Sahin.

Safety is a key factor for any potential vaccine because the shots will be given widely to healthy people. The Food and Drug Administration has said it will require two months of safety data before reviewing any application for emergency authorization for a vaccine. Collecting the extra safety data probably won’t cause much of a delay once readout on the vaccine’s effectiveness is available, stated Ugur Sahin. He further asserted “Waiting another couple of weeks to complete the safety data should not be a concern”.