Overall numbers of diarrhoea-related
hospitalizations from 1 January 2003
to 31 December 2011 were examined.
Because the catchment populations of
the study hospitals were not known,
rates of hospitalization for diarrhoea per
10 000 hospitalizations from all causes
were calculated. The median annual rate
of diarrhoea-related hospitalizations
during the baseline, “prevaccine” period
of 2003 to 2006 was compared with the
corresponding value for the “postvaccine”
period of 2008 to 2011. Since RVA
vaccination was still being rolled out in
Mexico during the year, 2007 was considered
a transitional year and excluded
from this part of the analysis.
Rate ratios (RR) were calculated
so that monthly and annual diarrhoearelated
hospitalization rates in each of
the postvaccine years could be compared
with the corresponding prevaccine rates.
The RRs were stratified by age group –
0–11, 12–23 and 24–59 months – and
socioeconomic category. Although RVA
testing or coding is not routinely conducted
in the study hospitals, in Mexico
approximately 60 to 70% of the hospitalizations
for laboratory-confirmed RVA
infection occur during the months of
December to May.19 Seasonal changes in
diarrhoea-related hospitalizations were
therefore specifically assessed before and
after the introduction of the RVA vaccine.
Ninety-five per cent confidence
intervals (95% CI) were calculated
around the relative reductions in the
rates of diarrhoea-related hospitalization.
Statistical significance in χ2
tests
was assessed. A P-value of less than 0.05