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COVID-19 Vaccine Trials: Reality Check

COVID-19 Vaccine Trials: Reality Check

There is both good and bad news with respect to the ongoing COVID-19 vaccine trials. As a preface, know that approximately 90% of vaccine trials fail to lead to production of a final vaccine, and 50% of those failures occur in phase 3. Usually, vaccine trials enroll a only few thousand participants who are followed for at least 5 years—observing for adverse events (AEs), efficacy, and durability. AEs usually, but not always, are revealed within the first 2 months of vaccine administration. These are just a few reasons why the COVID-19 vaccine trials are enrolling 30,000+ patients, largely intending to power the trials for efficacy and AEs.

The US has a robust cadre of COVID-19 vaccine trials from 18 different biopharmaceutical companies, three of which are currently in phase 3. A total of 179 vaccines are in development worldwide.

The vaccine being developed jointly by Pfizer and BioNTech is one of three vaccines in phase 3 trials—those being developed by Moderna and AstraZeneca/University of Oxford are the others. Both Pfizer/BioNTech and Moderna are utilizing completely new mRNA technology. Outside study groups have just released interim analyses of these two vaccines, and efficacy appears to be on the order of 95%—far higher than originally hoped for. If born out in subsequent analyses, this is encouraging news.

While exciting, remaining questions should temper enthusiasm. No data have been released; only press releases. And while the efficacy is impressive, it is preliminary and must be confirmed with subsequent analysis. These vaccines were only tested in adults, and the trials did not study children or adults with immunodeficiencies, so no conclusions can be drawn about these and other special populations. Although AEs were generally minor, it has not yet been 2 months since all participants received both doses, so the jury is still out on AEs. And durability—how long the vaccine might provide protection—remains unknown.

There is also a reality regarding the Pfizer vaccine that is often overlooked: it must be stored at extremely low temperatures, -94°F, making the logistics of transportation and administration problematic, at best. This implies that your neighborhood Walgreens may not be able to administer the vaccine, simply because they do not have the cold-storage capability. Thus Pfizer's vaccine may be only for those near major medical centers in densely populated cities. The good news is that the Moderna vaccine is stored at -4°F, making logistics similar to many other vaccines.

There is one very big question that has yet to be answered: Will people get a COVID-19 vaccine? Surveys show the number of Americans answering in the affirmative are dwindling. A Pew Research study published in mid-September reported dismal numbers, with only 51% of US adults saying they definitely or probably would get a COVID-19 vaccine, and 49% saying they definitely or probably would not. Just 32% of Black adults said they would definitely or probably get a COVID-19 vaccine. This bodes poorly for any COVID-19 vaccine and broad population immunity.


Filed under: Allergy/Immunology, Infectious Diseases, Preventive Medicine, Public Health

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