New Research Highlights Strengths & Weaknesses of the Flu Shot

The new weekly FluView report from the Centers for Disease Control and Prevention (CDC) for week 48 ending December 2, 2017, is reporting widespread flu activity in 7 states — Arkansas, Georgia, Louisiana, Massachusetts, Mississippi, Oklahoma, and Virginia – up from 4 states the previous week. High flu activity has continued in 3 states – Louisiana, Mississippi, and South Carolina – and laboratory testing of respiratory specimens shows that influenza A (H3N2) has continued to be predominant this flu season. In addition, 2 influenza-associated pediatric deaths were noted in the new surveillance report – one that occurred in week 45 due to influenza A and one that occurred in week 47 due to influenza B.

In its December 7th influenza update, the Connecticut Department of Public Health reported the state’s first flu death of the season. The victim was a state resident over 65 years of age; health officials have not released any other details. Connecticut health officials have reported that 77 patients have been hospitalized with the flu thus far this season, with 59 having fallen ill from influenza A. Furthermore, Connecticut has had 197 influenza positive laboratory tests.

Indiana’s State Department of Health has also reported its first flu death of the season. In a press release issued on December 8th, the department announced that the victim was a resident under the age of 18. “Unfortunately, we are already seeing some heartbreaking consequences of the flu in Indiana,” said Indiana state health commissioner Kris Box, MD. “With influenza activity on the rise, I encourage anyone who hasn’t gotten a flu shot to get one to help protect themselves and their loved ones.”

In flu research news, a new paper from researchers in Singapore suggests that flu vaccine effectiveness for some influenza A and influenza B viruses drops within 6 months of vaccination. The paper, published in The Journal of Infectious Diseases, was a review of 14 previously published studies that had been conducted that analyzed flu seasons ranging from 2009 to 2016. The studies included data on vaccine effectiveness in Europe, the United States, Kenya, Thailand, and Australia. The researchers found that the flu vaccine’s effectiveness against influenza A (H3N2) declines by 33% within 6 months of vaccination and by 19% for influenza B viruses. Furthermore, in tropical climates, where flu activity can persist year-round, the authors concluded that new vaccination strategies that recommend individuals receive a flu shot every 6 months may help control the virus.

In another recent study published in the same journal, researchers in Japan found that pregnant women who receive the flu shot during pregnancy, and postpartum women who are vaccinated while their infants are too young to receive a flu shot, impart a good amount of flu protection on to their babies. The study authors examined 3,441 infants born in 117 Osaka hospitals before the 2013-2014 flu season. They found that prenatal vaccination was 61% effective at preventing influenza in infants, whereas postpartum vaccination was 53% effective. Maternal vaccination was also associated with a reduction in flu-related hospitalizations in infants. “Pregnant women should receive influenza vaccination in order to protect not only themselves but also their infants. If they fail to receive influenza vaccination during pregnancy, postpartum vaccination would also be useful in protecting their infants from the threat of influenza," the authors wrote.

The CDC notes that the flu vaccine is safe for pregnant women as well as breastfeeding mothers, who can reduce their risk of catching the flu and passing it on to their infants by receiving a flu shot. The CDC recommends the flu shot for infants who are 6 months and older.