More data with more study designs
Dial Hewlett Jr., MD, medical director for disease control services, Westchester County Department of Health, White Plains, N.Y., said in an interview that the ethicists raise important issues that have been discussed in other forums, including a recent webinar of the National Academy of Medicine.
“As the authors point out, once you have a vaccine that has been shown to be effective and safe, it’s no longer ethical to enroll people in placebo trials,” he said.
Therefore, he said, Pfizer and Moderna will undoubtedly offer their vaccines to the people in their studies’ placebo groups after the vaccines receive an EUA. Then they will follow everyone who has been vaccinated for 2 years to determine long-term safety. Efficacy will also continue to be measured as an adjunct of safety, he said.
With regard to the difficulty of reconsenting individuals to enter a new clinical trial after a vaccine has been approved, he said, “I’d agree that trying to get all the same participants to come into another study would be a challenge. You can, however, design studies that will allow you to obtain the same information. You will have a large number of people out there who haven’t been vaccinated, and you can do single-arm longitudinal studies and measure a number of things in the individuals who are enrolled in those studies,” he said.
“You can look at the immunologic markers, both antibody and T-cell. You can follow these individuals longitudinally to see if they do develop disease over a period of time. If they do, you can determine what their levels of response were,” he added. “So there are opportunities to design studies that would give you some of the same information, although it would not be in the same population that was in the randomized trials.”
For newer vaccines that have yet to be tested, he said, developers can compare “historical controls” from the trials of approved vaccines, i.e., data from the unvaccinated participants in those studies, with the data from inoculating people with the novel agents. The historical data can be sex- and age-matched, among other things, to individuals in the new trials. Moreover, because the study protocols have been harmonized for all trials under Operation Warp Speed, it doesn’t matter what kind of vaccine they’re testing, he said.
It may be necessary to do additional studies to find out how long immunity lasts after people have been vaccinated, Dr. Hewlett pointed out.
“You may have a different trial design. You don’t need a control arm to determine how long immunity lasts. You’re just comparing the patients who were vaccinated to nothing,” he said. “So you could have a single-arm trial on a group of people who consent to be immunized and followed. You can see what their antibody levels are and other surrogate markers, and you can see when they might develop disease, if they do. You’d need a large sample, but you can do that.”
Dr. Hewlett noted that additional studies will be required to determine whether the new vaccines stop transmission of the coronavirus or just prevent symptoms of COVID-19. Until it’s established that a vaccine halts transmission or the country achieves herd immunity, he said, “we’ll still have to wear masks and take other precautions, because a significant portion of people will still be at risk.”