Last week Pfizer / BioNTech announced that its coronavirus vaccine will protect people for up to six months after the second dose. However, its effectiveness has been reduced from 95% in November 2020 to 91%. That doesn’t surprise Carlos Malvestutto, MD, an infectious disease expert at Ohio State University’s Wexner Medical Center. “Real-world efficacy is generally less than clinical trial efficacy in most cases because clinical trial participants are a select population of motivated individuals,” he said.

Dr. Malvestutto took the time to answer a few questions for Medical Daily.

Question: F. Why should the results of a real-world study be so different from those of a controlled study that involved tens of thousands of people?

A. Real efficacy is generally less than clinical trial efficacy in most cases because clinical trial participants are a select population of motivated individuals. The results of this observational study of healthcare workers are not far from estimates of the vaccine’s effectiveness in randomized clinical trials. You need to take into account the large confidence intervals of these estimates (68% -97%) for full vaccination and 59-90% for partial vaccination in order for actual efficacy to be somewhere within these confidence intervals. To me, these real-world efficacy studies confirm the high efficacy of the vaccine that has been reported in the clinical trials.[68%-97%)forfullvaccinationand59-90%)forpartialvaccinationsotheactualefficacyfallssomewherewithinthoseconfidenceintervalsTometheserealworldefficacytrialsconfirmthehighvaccineefficacyreportedintheclinicaltrials[68%-97%)forfullvaccinationand59-90%)forpartialvaccinationsotheactualefficacyfallssomewherewithinthoseconfidenceintervals Tometheserealworldefficacytrialsconfirmthehighvaccineefficacyreportedintheclinicaltrials

Question: F. Are you surprised by these results?

A. Not at all. These results are consistent with the vaccine’s excellent efficacy in the large Phase 3 clinical trials for the Pfizer and Moderna / BioNTech vaccines. It is also very encouraging to see that partial immunization can offer a very high level of protection. Other observational studies also consistently show high levels of effectiveness in all populations.

Question: F. The study was carried out from December to March. During that time the variants were out there. Does this fact mean that the mRNA platform is even better than the study results?

A. We know the clinical trials were conducted prior to the B1.117 and other varieties of concerns were circulating in the United States. This study will perform genomic sequencing of the virus to determine the prevalence of these variants, but we can assume that at least a significant proportion of the cases in this study were due to B1.117 and other new variants, confirming the conclusion that these vaccines are highly effective even in the presence of these new variants.

Question: F. There appear to be no similar studies with the J&J vaccine. Would you expect this vaccine to be similarly effective in a real-world setting?

A. We’ll eventually see similar studies for the J&J vaccine. It got emergency approval last month and was only recently given, so not enough people have been vaccinated with this vaccine to conduct a real efficacy study. I am sure we will have similar data on this vaccine in the future.

Carlos Malvestutto, MD, is an infectious disease specialist at Ohio State University’s Wexner Medical Center. Ohio State University
Carlos Malvestutto, MD, an infectious disease expert at Ohio State University’s Wexner Medical Center.