Effect of Rotavirus Vaccination on Death from Childhood Diarrhea in México Vesta Richardson, MD July 2010, Johannesburg, Southafrica
Background Pre-licensure trials did not assess the effect of rotavirus vaccination on mortality from diarrhea. Public health priority: Will the use of these vaccines prevent/decrease diarrhea related deaths? In addition to other crucial interventions: Improved sanitation, safe water, promotion of breast feeding, oral rehydration and vitamin A supplementation.
Mexico 2006 Rotarix: Protective efficacy of 85% against severe rotavirus disease and of 42% against severe diarrhea from any cause. Annual birth cohort ~ 1.9 million infants Three health care institutions: Ministry of health (50%), IMSS (43%), ISSSTE (7%) Phased introduction of a monovalent rotavirus vaccine: 5% of children in impoverished states (Feb.2006) IMSS children in November 2006 (43% of children) Universal for all children as of May 2007 (2 and 4 months)
Vaccine coverage in Mexico: Methods 1) Administrative method (crude estimate of coverage):. Annual number of doses administered i d (1 st and d2 nd ). Birth cohort (eligible to receive vaccine purchased through CENSIA) Vaccine coverage by age group (< 11 months, 12-23 months old) at the end of 2007, to estimate children potentially protected during 2008 2) Computerized data (nationwide) as of 2010. 3) Diarrhea-related deaths: Official Data (INEGI/DGIS): January 2003 May 2009
Methods Effect of rotavirus vaccine: 2007 was a transitional year (universal vaccination as of May 2007) Comparison between rate of diarrhea-related deaths in 2008/2009 and baseline data from 2003 2006. Comparison between absolute number of diarrhea-related deaths during the peak rotavirus-season (Dec - May in 2008 and 2009) and median number of deaths during same period in baseline years Statistical analysis: Stratified by age group (0-11 mo, 12-23 mo, 24-59 mo) Chi-square test 95% CI for reduction in death rate
Results Vaccine coverage by January 2008: Age 1st dose 2nd dose < 11 months 12-23 months 74% 51% 4% 2% Vaccine coverage by January 2009: Age 1st dose 2nd dose < 11 months 81% 73.7%
Results All diarrhea-related related deaths in children under 5 years, Mexico, Baseline years 2003 2006 Rate of death: 18.1 x 100 000 N= 1793 annual median
Number of diarrhea realted deaths among children 59 months of ageor younger from Number of diarrhea realted deaths among children 59 months of age or younger from July 2002 through Apr 2010 in Mexico, according to age group.
Results Changes in Diarrhea-Related Mortality among Children 59 Months of Age or Younger in 2008 in Mexico, as Compared with the Baseline Period (2003 2006), According to Age Group.
Results No. diarrhea death hs 200 180 160 140 120 100 80 60 40 20 0 Jan-2007 Country-wide vaccine introduction, May, 2007 Feb Mar Apr May Jun Jul Aug Sep Oct Nov Age 0-11 months Dec Jan-2008 Feb Mar Apr May Jun Jul Aug Sep Oct 2007-2009 observed deaths 2003-2006 maximum 2003-2006 median 2003-2006 minimum Nov Dec Jan-2009 Feb Mar Apr May Number of Diarrhea- Related Deaths per Month among Children 23 Months of fage or Younger after the Introduction of Rotavirus Vaccination in Mexico, as Compared with the Baseline Period (2003 2006).
Results Number of Diarrhea-Related Deaths among Children 23 Months of Age or Younger during Rotavirus Seasons in 2008 and 2009, as Compared with the Baseline Period (2003 2006).
Results All diarrhea-related deaths in children under 5 years, Mexico, Baseline years 2003 2006 Post Vaccine 2008 2009 Rate of death: 18.1 x 100 000 N= 1793 annual al median Rate of death: 11.8 x 100 000 N=1118 annual median
Main causes of infant mortality (children 0 to 11 months) Mexico 2000-2009
Discussion Monovalent rotavirus vaccine has probably contributed to a reduction in deaths related to diarrhea from any cause among Mexican children Reduction of 66% of deaths in < 11 months and in 12-23 month old notable blunting of the typical seasonal peak in diarrhea-related deaths during two consecutive rotavirus seasons (Dec-May, when 68% of laboratory confirmed cases occur) after vaccine made universal. Ecologic analysis cannot provide definitive evidence that vaccination prevented deaths Substantial decline of 29% yearly in mortality from diarrhea from any cause in children between 12 and 23 months of age raises the possibility that vaccination may have reduced transmission of rotavirus disease in Mexico and induced herd protection.
Discussion Caveats: Vaccine coverage not precise, but useful estimation. Verified by annual coverage surveys. Possible secular trends in disease. Underreporting of diarrhea-related deaths likely, but similar throughout the years Rotavirus not confirmed through fecal specimens, but marked seasonality Case-control studies are more specific, but entail challenges currently under way
Discussion If the reduction in disease is sustained during future years, these data will provide an estimate of the vaccine-preventable burden of childhood diarrhea-related related deaths attributable to rotavirus before the introduction of vaccine. Routinely collected data on mortality related to diarrhea from any cause could prove to be a useful source of monitoring of the effect of rotavirus vaccination.
Main causes of infant mortality (children 0 to 11 months) Mexico 2000-2009 2009