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05-01-2012 | Gynaecology | Article

Infant group B streptococcal infection rates highest in Africa


Free abstract

MedWire News: Results from a systematic review and meta-analysis show that global rates of group B streptococcus (GBS) infection in infants are highest in Africa and lowest in Asia, but better quality data is needed to formulate effective prevention policies.

"Despite widespread use of intrapartum antibiotic prophylaxis, GBS remains a leading cause of morbidity and mortality in infants in Europe, the Americas, and Australia," note Karen Edmond (London School and Hygiene and Tropical Medicine, UK) and colleagues.

However, estimates of disease burden in many countries outside of these regions is not available, they add.

Edmond and team therefore estimated the global incidence of invasive GBS and case fatality in infants aged 0-89 days in the era of intrapartum prophylaxis (2000-2011). They also examined serotype distribution of group B streptococcus isolates.

The researchers identified 56 studies that reported incidence of GBS, 29 that reported case fatality, and 19 that reported serotype distribution. An additional search for studies that reported serotype distribution from 1980 onwards yielded a total of 38 articles.

As reported in The Lancet, the mean GBS incidence in infants aged 0-89 days was 0.53 cases per 1000 live births, and the mean case fatality ratio was 10%.

Incidence was highest in Africa (1.21 cases per 1000 live births) and lowest in South-East Asia (0.02 cases per 1000 live births). "The low incidence in Asia could be a true regional estimate or could be due to high previous antibiotic use, high case fatality before specimen collection, or study design issues including small sample sizes and incomplete periods for data collection," the researchers note.

Africa also had the highest case fatality ratio, at 22%, compared with 9% in Asia.

Incidence rates in the Americas (0.67 cases per 1000 live births) and Europe (0.57 cases per 1000 live births) were higher than the global average, but while case fatality in the Americas was similar to the global average (11%), in Europe it was lower (7%).

When the researchers compared early- (0-6 days) and late-onset (7-89 days) GBS, they found that the incidence and case-fatality of early-onset disease was around twice that of late onset disease, at 0.43 versus 0.24 cases per 1000 live births, and 12.6% versus 4.6%, respectively.

Serotype III (48.9%) was the most frequently identified serotype in all regions with available data followed by serotypes Ia (22.9%), Ib (7.0%), II (6.2%), and V (9.1%). Serotype distribution was similar across all regions and has not changed since 1980, the team observed.

This indicates that "a conjugate vaccine incorporating five serotypes (Ia, Ib, II, III, V) could prevent over 85% of global group B streptococcal disease in infants aged younger than 3 months," the researchers suggest.

The use of any intrapartum antibiotic prophylaxis (reported by 69% of studies) was associated with lower incidence of early-onset GBS, at 0.23 cases per 1000 live births, than non-use of prophylaxis, at 0.75 cases per 1000 live births.

Furthermore, intrapartum antibiotic prophylaxis use was the only variable significantly associated with the risk for early-onset disease; early-onset GBS was 2.2 times more likely to occur when prophylaxis was not used.

Since studies from low-income countries contributed just 5% weight to the meta-analysis, "high-quality group B streptococcus data are urgently needed from low-income countries, especially from Asia," say Edmond et al.

They conclude: "These data are required to formulate prevention policies including the optimum use of intrapartum antibiotic prophylaxis and the potential use of group B streptococcus vaccines."

By Laura Dean

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