The current flu season should have provided the first opportunity to gauge the impact of quadrivalent vaccines. However, the extra B strain in the quadrivalent vaccines has been rendered irrelevant by the almost total dominance of H1N1.
In an interim report on vaccine effectiveness, the Centers for Disease Control and Prevention (CDC) notes that the H1N1 virus that caused the 2009 pandemic accounted for 98% of all strains detected this flu season. The strain was included in trivalent and quadrivalent vaccines, meaning any of the products from AstraZeneca ($AZN), GlaxoSmithKline ($GSK), Novartis ($NVS), Sanofi ($SNY) and others should have provided protection. In previous years the prevalence of strains not included in vaccines has caused the effectiveness of the shots to sink to 30% and strengthened the case for quadrivalent shots that offer broader protection.
The CDC estimates that the current crop of vaccines cut the risk of having to visit the doctor with flu by 61%. While the figure is an improvement on previous years--including the 52% protection provided by the 2012-13 flu vaccines--it is still well short of what CDC wants to see. "It's not working as well as we wish it would," CDC Director Dr. Tom Frieden said at a media briefing attended by the Los Angeles Times. Frieden said CDC is committed to supporting the development of better flu vaccines, but for now the trivalent and quadrivalent shots are the best way of preventing illness.
In the near term, increasing the proportion of people receiving the vaccine offers the best hope for cutting the number of flu cases and deaths. Almost two-thirds of flu-related hospitalizations this winter occurred in people aged 18 to 64 years old. While most seniors receive the flu vaccine--and many children too--immunization rates among adults aged 18 to 64 are low. The CDC recommends that everyone aged 6 months old and up receive the flu vaccine, but it is falling well short of this goal. As of mid-November, just 41% of pregnant women, a group CDC strongly encourages to receive the vaccine, were immunized.