Week's news analysis

Pfizer's Covid-19 vaccine candidate:
what are the next steps?

By The Editor - 10 November 2020

Results from the first interim analysis of a Phase III study of Pfizer and BioNTech 's BNT162b2 have raised huge enthusiasm all over the world as the pandemic is speeding up, forcing governments to enact new lockdowns. The vaccine is the first to be tested in the United States and to generate late-stage data.

According to the two partners, the experimental mRNA-based vaccine candidate is more than 90 % effective in preventing Covid-19 in participants without evidence of prior infection, at 7 days after the second dose. This means that protection is achieved 28 days after the initiation of the vaccination, which consists of a 2-dose schedule. The study, rolled out in July, has enrolled 43,538 participants to date.

Even if the first results are promising, caution is necessary in order to accumulate further data. While the original interim analysis was scheduled to be conducted after 32 confirmed cases of Covid-19 in trial participants, this was increased to a minimum of 62 cases, before eventually reaching 94.

As the Phase 3 study is ongoing, further new data could affect results. It is not yet known how well BNT162b2 works in certain subgroups (elderly or higher-risk people for instance), as these analyses have yet to be conducted. It also remains unknown whether the vaccine prevents severe disease, as none of the participants who got Covid-19 in the interim analysis had severe cases. It's also unclear if the vaccine simply prevents symptoms in mild or moderate cases, or if it reduced severe outcomes. Moreover, it is not clearly established how long this protection lasts, if the vaccine candidate will become a yearly or seasonal immunization and if it causes sides effects.

In the coming weeks, the study will continue through to its final analysis at 164 confirmed cases, while participants will be monitored for long-term protection and safety for an additional two years after the second dose.

Pfizer and partner BioNTech will not apply for FDA emergency-use authorisation (EUA) for BNT162b2 until a key safety milestone is met, which is expected to be in the third week of November. At this time, Pfizer expects to have the two-month safety data required by regulators on half the volunteers in the study following their second dose.

Distribution challenges are likely to become big issues for the drugmanufacturers. The vaccine must be stored at super-cold temperatures (minus 94 degrees Fahrenheit) which could make it extremely difficult to deliver to many places. Pfizer and BioNTech say they are confident those issues can be managed. Their plan includes shipping containers that can keep doses at that temperature for 10 days. Pfizer has lined up additional locations in Wisconsin and Germany for storage.

Pfizer seems to lead the race so far as former vaccine front runner Moderna does not expect to have the trial data required to go for approval until November 25 Meanwhile, AstraZeneca's partnership with the University of Oxford expects results by the end of this year.

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