This article is in response to “Rotavirus vaccine: tortured data analyses raise false safety alarm”, June 22, 2024 by R. Prasad
A study reported in New England Journal of Medicine (NEJM) found no risk of intussusception from Rotavac, a rotavirus vaccine manufactured by Bharat Biotech. Using a self-controlled case series (SCCS) they claimed that the risk of intussusception (where the intestine telescopes into itself and gets obstructed) in the 21 days after any dose of the vaccine was comparable to the background risk.
Using the same raw surveillance data, we demonstrated a very significant increase in risk that was missed in the previous analysis. We published the study in the peer-reviewed International Journal of Risk & Safety in Medicine.
In our analysis, at first, we looked at the age of intussusception among the vaccinated compared to the unvaccinated. We found that intussusception occurred significantly earlier in the vaccinated. For this reason, we concluded that the unvaccinated are not an appropriate control group for further analysis.
The original study mistakenly used these unvaccinated in their controls. We did the same SCCS analysis as done by the NEJM authors, after removing the unvaccinated from the analysis and found the risk of intussusception increased to nearly 2.5 times within 21 days after the third dose.
In addition, we used other statistical tools. To minimize confounding by age, we used the self-controlled risk interval (SCRI) method, which compares the incidence of an adverse event during a high-risk period to the incidence during a control period closer in time to the vaccination. We limited the observation period to 180 days of age because intussusceptions are rare during this period. We found a 1.6-fold increase in risk of intussusception after any dose of the vaccine.
The number of babies developing intussusceptions was highest within a month after vaccination, with risks tapering off over time. There were 93 cases of intussusception in the first 30 days compared to 63 in the next 30 days. This was statistically very significant and suggested vaccine-risk, much like the SCRI and SCCS analyses. In these multiple analyses, we see the same risk and this buttresses our conclusion.
When all tests point to an increased risk of intussusception, the results cannot be ignored as having occurred by chance. Our study has shown it was inappropriate to use unvaccinated babies as controls because the age of intussusception is lower in the vaccinated.
(This article has received a response, published here.Brian Hooker is Chief Scientific Officer, Children’s Health Defence New Jersey, and Emeritus Professor of Biology Simpson University, Redding, California, U.S. and Jacob Puliyel is a paediatrician who was formerly a Member of the National Technical Advisory Group on Immunisation of the Government of India. We were co-authors of the study published in the International Journal of Risk & Safety in Medicine.)
