ARCHIVED - Infectious Diseases News Brief - November 23, 2012
Malaria prevention in pregnancy, birthweight, and neonatal mortality: a meta-analysis of 32 national cross-sectional datasets in Africa
Low birthweight is a significant risk factor for neonatal and infant death. A prominent cause of low birthweight is infection with Plasmodium falciparum during pregnancy. Antimalarial intermittent preventive therapy in pregnancy (IPTp) and insecticide-treated mosquito nets (ITNs) significantly reduce the risk of low birthweight in regions of stable malaria transmission. The researchers aimed to assess the effectiveness of malaria prevention in pregnancy (IPTp or ITNs) at preventing low birthweight and neonatal mortality under routine programme conditions in malaria endemic countries of Africa.
They used a retrospective birth cohort from national cross-sectional datasets in 25 African countries from 2000—10. The researchers used all available datasets from multiple indicator cluster surveys, demographic and health surveys, malaria indicator surveys, and AIDS indicator surveys that were publically available as of 2011. They tried to limit confounding bias through exact matching on potential confounding factors associated with both exposure to malaria prevention (ITNs or IPTp with sulfadoxine—pyrimethamine) in pregnancy and birth outcomes, including local malaria transmission, neonatal tetanus vaccination, maternal age and education, and household wealth. They used a logistic regression model to test for associations between malaria prevention in pregnancy and low birthweight, and a Poisson model for the outcome of neonatal mortality. Both models incorporated the matched strata as a random effect, while accounting for additional potential confounding factors with fixed effect covariates.
The researchers analysed 32 national cross-sectional datasets. Exposure of women in their first or second pregnancy to full malaria prevention with IPTp or ITNs was significantly associated with decreased risk of neonatal mortality (protective efficacy [PE] 18%, 95% CI 4—30; incidence rate ratio [IRR] 0-820, 95% CI 0-698—0-962), compared with newborn babies of mothers with no protection, after exact matching and controlling for potential confounding factors. Compared with women with no protection, exposure of pregnant women during their first two pregnancies to full malaria prevention in pregnancy through IPTp or ITNs was significantly associated with reduced odds of low birthweight (PE 21%, 14—27; IRR 0-792, 0-732—0-857), as measured by a combination of weight and birth size perceived by the mother, after exact matching and controlling for potential confounding factors.
Malaria prevention in pregnancy is associated with substantial reductions in neonatal mortality and low birthweight under routine malaria control programme conditions. Malaria control programmes should strive to achieve full protection in pregnant women by both IPTp and ITNs to maximise their benefits. Despite an attempt to mitigate bias and potential confounding by matching women on factors thought to be associated with access to malaria prevention in pregnancy and birth outcomes, some level of confounding bias possibly remains.
Polio cases worldwide reached historic lows in 2012, and for the first time there were no new outbreaks beyond countries already harboring the disease, leaving researchers confident that a massive and re-energized international campaign to eradicate polio is on a path to success, according to presentations at the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH). Globally there were 177 polio cases through October 2012, a drop from 502 during the same period last year. Despite the dramatic drop, polio experts noted challenges in Pakistan posed by parents who refuse to vaccinate their children and in Nigeria where polio cases more than doubled in 2012 and threatened to re-infect currently polio-free countries. Pakistan, Nigeria and Afghanistan are the only countries where polio remains endemic and are the battle grounds of efforts to make polio only the second human disease, after smallpox, to be completely eliminated. Steven Wassilak, MD, a medical epidemiologist and polio expert at the US Centers for Disease Control and Prevention (CDC), said new data from Pakistan show that of the two types of wild polio virus (WPV1 and WPV3) circulating in the country, the one known as WPV3 - or Type 3 - is close to being eliminated. The CDC's Wassilak said the refusal by parents in Pakistan and Nigeria to vaccinate their children presents a challenge to eradication. But Wassilak said vaccine refusal is not an insurmountable barrier to global eradication. "We saw similar problems in India, and while they were not resolved overnight, eventually we saw immunization coverage increase and polio cases halted," he said. "It requires working more closely with community leaders and greater political commitment at all levels, which is what we are seeing in both Pakistan and Nigeria." India has not reported a polio infection since January 2011 and the entire Southeast Asia Region of WHO could be certified polio-free in 2014 if no new cases arise. Wassilak said advisors from India are now working in Nigeria to share their lessons learned. Meanwhile, the CDC is providing technical support to the global eradication effort, tracking the different types of polio that are circulating in the affected countries and training volunteers to assist in polio vaccination campaigns.
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