Vaccine's 95% effectiveness 'good news' but 'key question' surrounding threshold of immunity remains

Vaccine's 95% effectiveness 'good news' but 'key question' surrounding threshold of immunity remains

File image. Credit: PA Wire.

A University College Cork (UCC) senior lecturer has said that final results from the late-stage trial of Pfizer’s Covid-19 vaccine showing 95% effectiveness is “good news” but that all results will have to be reviewed before distribution of the vaccine is allowed.

Final results from the company’s late-stage trial of its Covid-19 vaccine, developed with German partner BioNTech, show it was 95% effective and that the safety data milestone required by US Food and Drug Administration (FDA) for Emergency Use Authorization (EUA) has been achieved.

170 confirmed cases of Covid-19 were evaluated with 162 observed in the placebo group versus eight in the vaccine group.

Efficacy was consistent across age, gender, race and ethnicity demographics with observed efficacy in adults over 65 years of age of over 94%.

Data also demonstrated that the vaccine was well tolerated across all populations with over 43,000 participants enrolled with no serious safety concerns observed.

The final analysis comes just one week after initial results from the trial showed the vaccine was more than 90% effective.

On Monday, Moderna released preliminary data for its vaccine, showing similar effectiveness.

Speaking to The Echo, senior lecturer at the School of Biochemistry and Cell Biology at UCC, Dr Anne Moore, said that the consistent effectiveness across all ages “gives some hope that it will protect the elderly as well”.

Dr Anne Moore, University College Cork, Senior Lecturer in Biochemistry and Cell Biology. Photo by Tomas Tyner, UCC.
Dr Anne Moore, University College Cork, Senior Lecturer in Biochemistry and Cell Biology. Photo by Tomas Tyner, UCC.

She said, however, that although the safety data milestone required by the FDA was met, that a vaccine will not be distributed until Pfizer submits all results to the FDA for review.

“Let's say if there was a safety signal in the elderly or HIV-infected then they wouldn’t be authorised to use it in their populations but from what Pfizer are saying they don’t see safety signals that warrant a red flag in any of their populations which is good,” she said.

Dr Moore said that “there is still a lot to be done” and that a key question around the threshold of immunity remains unanswered.

“All we know is that soon after vaccination you will be protected, the key question is what is the threshold of immunity that you need to be protected, if that's very low, then we can be more optimistic that the vaccines will work for longer because it will take longer before those immune responses go down to that sub-threshold and that's an absolutely key question that we need to address,” she said.

Both the Pfizer vaccine and the Moderna vaccine have been developed with new technology known as messenger RNA (mRNA).

Special lecturer in advanced therapies at UCC's School of Pharmacy, Dr Piotr Kowalski, explained what the mRNA technology is about.

“Therapies utilizing the delivery of messenger ribonucleic acid (mRNA) to patients’ cells have many potential applications in vaccine development and gene therapy. The first clinical application of mRNA will clearly be vaccinations.

How mRNA vaccines work. Credit: Duncan Mil/Graphic News.
How mRNA vaccines work. Credit: Duncan Mil/Graphic News.

“Traditional vaccines utilize the inactivated virus or antigen protein itself, manufactured in a cell-based process that takes months to set up and run. With mRNA vaccines, the patient’s own body becomes the antigen factory.

“The speed with which mRNA vaccine candidates can be designed and produced is a key advantage of this new vaccine technology, for Moderna, it took a total of 25 days from sequence selection to vaccine manufacture.

“Everybody is looking for the clinical data, and so far, the data for mRNA vaccines against SARS-CoV-2 from BioNTech and Moderna look very promising,” he said.

Ugur Sahin, MD, CEO and Co-founder of BioNTech, said that the achievements “highlight the potential of mRNA as a new drug class”.

“Our objective from the very beginning was to design and develop a vaccine that would generate rapid and potent protection against COVID-19 with a benign tolerability profile across all ages. We believe we have achieved this with our vaccine candidate BNT162b2 in all age groups studied so far and look forward to sharing further details with the regulatory authorities,” he said.

File image.
File image.

Mr Sahin thanked those who contributed to the “historically unprecedented achievement”.

The Phase 3 clinical trial began on July 27 and has enrolled 43,661 participants to date, 41,135 of whom have received a second dose of the vaccine candidate as of November 13.

Approximately 42% of global participants and 30% of US participants have racially and ethnically diverse backgrounds, and 41% of global and 45% of US participants are 56 to 85 years of age.

Chairman and CEO of Pfizer Dr Albert Bourla said that the results mark “an important step” in bringing forward a vaccine “capable of helping to end this devastating pandemic”.

“With hundreds of thousands of people around the globe infected every day, we urgently need to get a safe and effective vaccine to the world,” he said.

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