Maternal flu vaccine offers limited protection for newborns
Infants receive seasonal flu immunity through maternal influenza vaccines, but previous studies have not established how long this protection lasts. A study yesterday in JAMA Pediatrics—the largest of its kind to date—shows that infant immunity peaks by 8 weeks after birth and wanes significantly during the first 6 months of life.
Researchers in South Africa compared 1,026 infants whose mothers received a trivalent inactivated influenza vaccine during the last trimester of pregnancy with 1,023 infants whose mothers were unvaccinated and followed the groups for 6 months after birth. The vaccine was most effective between birth and 8 weeks (85.6% effective). Between 8 and 16 weeks, the efficacy dropped to 25.5% and was 30.3% effective by 24 weeks. The drop in protection correlated with a decrease in maternally derived influenza antibodies.
Pregnant women are a targeted population for influenza vaccines; both pregnant women and newborns are at risk for severe complications from the flu, including hospitalization and death. No flu vaccine is approved for use in infants younger than 6 months, so newborns must rely on the passive protection offered by maternal vaccination.
In an editorial on the study, Flor M. Munoz, MD, of Baylor College of Medicine in Houston, says the study shows infant protection is more dependent on transplacental antibodies than previously thought. Munoz calls this research provocative as breastfeeding—and the antibodies contained in breast milk—was considered the main route of protection for infants.
The authors of the study say their research shows the need for better maternal flu vaccines. "More immunogenic vaccines that can generate a protective immune response in infants, beginning at 8 weeks of age, need to be identified," the authors conclude.
Jul 5 JAMA Pediatrics study
Jul 5 JAMA Pediatrics editorial
Update: More than 40,000 new cases of chikungunya, mostly in Brazil
The Pan American Health Organization (PAHO) reported 43,842 new chikungunya cases as of Jul 1, bringing the 2016 total in the Americas to 193,245 infections.
In the previous update, posted Jun 24, there were only 950 new cases. PAHO's update last week reported increases of 28,493 and 15,347 suspected and confirmed cases, respectively.
Brazil reported the vast majority of the week's new cases, 39,084, bringing its cases for the year to 122,762. Bolivia was next, with 2,510 new cases and 18,398 for the year. Also of note, Honduras had 1,720 new cases as of Jul 1 and 12,053 total.
PAHO reported 1 new chikungunya-related death in Nicaragua, raising that number to 18 for the year, 16 of which have been in Brazil.
The outbreak began in December 2013 on St. Martin in the Caribbean with the first recorded cases of the disease in the Americas. Since then PAHO has reported 2,073,212 suspected or confirmed cases, including 286 deaths.
Jul 1 PAHO report
Officials report 16 H5N1 outbreaks in Cameroon affecting 34,000 birds
The World Organization for Animal Health (OIE) this week reported 16 new outbreaks of highly pathogenic H5N1 avian flu in Cameroon. The outbreaks began in mid-May through early June.
Twelve of the outbreaks were reported on farms, with a commercial farm in Bayangam in Ouest region reporting 1,500 cases, and 10,500 destroyed broilers on May 31. Another farm in the New Bell area of Douala, the capital, had an outbreak on Jun 1 that resulted in 1,439 cases and the destruction of 4,561 broilers, cockerels, and laying hens. A farm in Bilon in Sud region reported 2,000 cases on May 31, with 2,650 birds culled.
Three outbreaks occurred at markets, the largest at the Mvog-Ada market in Yaounde, Centre region. The market reported 682 cases in chickens of different ages on May 21. Another 382 birds were destroyed. The Marche Oyenga (Sud region) and the Cassablanca market (Oest) also reported scores of cases on May 21 and May 31, respectively
The total number of cases in the 16 outbreaks was 7,040, with 26,981 birds destroyed, for a total of 34,157 poultry deaths. The OIE reports unknown or inconclusive sources for the outbreaks, which are part of a wider resurgence of H5N1 in several parts of Africa this year.
Jul 4 OIE report