Comment on: Evolution of multiple sclerosis in France since the beginning of hepatitis B vaccination
We would like to comment on the interesting paper by Le Houe’zec concerning a relationship between hepatitis B (HB) vaccination and a subsequent risk of multiple sclerosis (MS) recently published in your Journal.1 The author states that this link is proven and that it could be causal.
Considering the immunization mass campaign which occurred in France between 1994 and 1997 as a “natural experiment” is an excellent idea. But to consider “quasi experiment” as an experimental design and to eliminate possible confounders, the analysis must rely on very precise data, both on population at risk as a whole and on individuals who have been or not been vaccinated.
The paper relies on an ecological analysis derived from two sets of medico-administrative data bases, namely those of the French health insurance system (CNAM) and of spontaneous post-vaccine reports to the French pharmacovigilance agency, which both concern the French population as a whole and no data collected on individuals....