I note the conclusion of this study by Tozzi, Bisiacchi, Tarantino,
De Mei, D'Elia, Chiarotti and Salmaso [1]. However, I also note the
limitations of the study as described in the discussion:
'Some limitations should be considered in the interpretation of our
results. The cumulative intake of thimerosal was relatively low, compared
with that in other countries including the United States, where
vaccination schedules included more thimerosal-containing vaccines in the
first year of life. Moreover, there was no comparison group with no
exposure to thimerosal, although our setting was appropriate to identify a
dose response effect in the absence of any evidence suggesting a threshold
dose for observation of an effect. Our analysis included only healthy
children who were selected during enrollment in the original trial, and
some families might have declined to participate in the present study
because their children had cognitive developmental problems. This might
have reduced the prevalence of adverse neuropsychological conditions and
might have made potential differences hard to detect. The eligibility
criteria of the original trial also limited the participation of low birth
weight children, and only 55 children with birth weights of <2500 g
underwent the neuropsychological evaluation (data not shown). Moreover,
only 1% of children in this study received hepatitis B virus vaccine at
birth. Although no effect of birth weight according to thimerosal intake
was detected through multivariate analyses, our study was not powered to
detect an association of thimerosal exposure and neuropsychological
development in low birth weight infants.' [1]
I ask how it would be possible to draw any useful scientific
conclusions from a study with such deficiencies in relation to the issues
it purportedly set out to investigate? But I also reflect on the headline
value of negative results for wider media consumption, as in the
Associated Press report by Carla K Johnson, with contributions from
Alberto Tozzi himself, Jennifer Pinto-Martin and Paul Offit [2] claiming
this strengthens the evidence base for vaccine safety.
[1] Alberto Eugenio Tozzi, Patrizia Bisiacchi, Vincenza Tarantino,
Barbara De Mei, Lidia D'Elia, Flavia Chiarotti, and Stefania Salmaso,
'Neuropsychological Performance 10 Years After Immunization in Infancy
With Thimerosal-Containing Vaccines', Pediatrics 2009; 123: 475-482.
[2] Carla K Johnson, 'Study adds to evidence of vaccine safety',
Associated Press,
http://www.google.com/hostednews/ap/article/ALeqM5jp7ZD1RFVm7yOzgaB04Ra4dY_ZuQD95UKPPG0
Conflict of Interest:
Parent of an autistic son
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