2011-12 flu vaccine effectiveness low, especially in repeat vaccinees
The flu vaccine was 47% effective against medically attended flu for all influenza strains in the 2011-12 season, and being vaccinated the year before lowered effectiveness, according to a study yesterday in Clinical Infectious Diseases.
US researchers from the Centers for Disease Control and Prevention and elsewhere looked at complete data for the season, which was relatively mild and peaked late. They found an overall vaccine effectiveness (VE) of 47% for preventing medically attended flu.
VE against 2009 H1N1 was 65%, but against H3N2, which was the predominant strain during the 2011-12 season. VE was only 39%. Its effectiveness against type B strains was 58% but was actually lower against the Victoria strain included in the vaccine (52%) compared with the Yamagata strain not included in the vaccine (66%).
The investigators also noted a statistically significant difference between VE for those who received a flu vaccine the year before (33%) and those who did not (56%).
In an accompanying commentary, Kathleen Neuzil, MD, MPH, of PATH in Seattle and John C. Victor of the University of Washington School of Medicine point out that the findings of reduced VE in those who were vaccinated the previous year were also noted in a study of flu VE in 2010-11 published in February (see story below).
They write, "The finding raises serious questions regarding the complicated interplay that occurs between our immune systems and repeated annual exposure to influenza antigens in current vaccines and/or potential exposure to wild‐type influenza virus."
Nov 13 Clin Infect Dis abstract
Nov 13 Clin Infect Dis commentary landing page
Mar 1 CIDRAP News story "Study: Getting flu shot 2 years in a row may lower protection"
2 more H5N1 cases in Cambodia, 1 fatal
Two new cases of H5N1 avian influenza have been reported in Cambodia, one in a child and one in an adult who has died of the disease, according to a joint release today from the World Health Organization (WHO) and the Cambodian health ministry.
The child is a 3-year-old boy from Kampong Speu province now hospitalized in critical condition in Phnom Penh. The other case-patient was a 29-year-old man from Pailin province; he died Nov 6. Both had had contact with sick and dead poultry.
The new cases bring the total for Cambodia to 26 this year and 47 since 2005, 35 in children younger than 14. Deaths from H5N1 this year in the country, according to a story from Xinhua, China's official news agency, number 14; total deaths since 2005 stand at 33.
Rapid response teams from the health ministry as well as representatives from Cambodia's Animal Health Task Force are investigating contacts of the new case-patients, looking for potential epidemiologic links among this year's H5N1 cases in the country, and implementing control measures and preventive treatment. Parents and guardians continue to be urged to keep children away from sick or dead chickens and ducks and to wash hands with soap after any contact with poultry.
Nov 14 WHO/Cambodia Health Ministry press release
Nov 14 Xinhua story
Study on first H6N1 case shows close ties to avian virus
An epidemiologic analysis today of the first and only known human case of infection with the H6N1 virus—which was first reported by Taiwanese officials in June—showed the isolate closely matched H6N1 viruses in poultry in Taiwan, according to a study today in The Lancet Respiratory Medicine.
An unsubtyped influenza A isolate from the 20-year-old woman's throat swab was sent to the Taiwan Centres for Disease Control and analyzed. "Sequence analyses showed that this human isolate was highly homologous to chicken H6N1 viruses in Taiwan and had been generated through interclade reassortment," the researchers wrote.
They said that the virus had a G228S substitution in the hemagglutinin (HA) protein that might help it attach better to human receptor cells.
The team conducted a contact and environmental investigation and collected clinical specimens from the woman and any symptomatic contacts. They were unable to pinpoint the source of her infection.
The authors conclude, "Our report highlights the continuous need for preparedness for a pandemic of unpredictable and complex avian influenza."
Nov 14 Lancet Respir Med abstract
Jun 21 CIDRAP News story "Taiwan reports first human H6N1 infection"
VLP H7N9 vaccine with adjuvant sparks strong immune response
An experimental virus-like particle (VLP) H7N9 influenza vaccine made by Novavax produced a strong immune response in early clinical trials when combined with an immune-boosting adjuvant but a much lower immune response when used without an adjuvant, according to a letter yesterday in the New England Journal of Medicine from Novavax scientists.
The researchers enrolled 284 adults in a randomized, placebo-controlled trial. Volunteers received two doses 3 weeks apart of either the VLP vaccine alone with either 15 or 45 micrograms (mcg) of HA, or with 5 or 15 mcg of HA combined with 30 or 60 units of the saponin-based Iscomatrix adjuvant.
Seroconversion and HA-inhibition (HAI) antibody titers of 40 or more were detected in 5.7% and 15.6% of participants receiving 15 mcg and 45 mcg of HA, respectively, in the unadjuvanted vaccine. In contrast, more than 60% of participants in three of the four adjuvant groups had HAI seroconversion and titers of 40 or more, with the highest level—80.6%—detected in those receiving 5 mcg of HA with 60 units of adjuvant.
The researchers also reported a good safety profile for all versions of the VLP vaccine.
Nov 13 N Engl J Med letter
Cell-culture Flublok vaccine made available
The US Food and Drug and Drug Administration (FDA) yesterday made Flublok, the country's first approved cell-based flu vaccine, available to the public, the vaccine's maker, Protein Sciences Corp. of Meriden, Conn., said in a press release.
Flublok is made by using a baculovirus to infect insect cells and cause them to produce the influenza protein HA. It is made without the use of eggs, and in June a federal advisory panel recommended its use for people with egg allergies. The FDA has approved it for adults 49 years old and younger.
The press release said that quantities of the vaccine are limited and will be distributed on a first come, first served bases. The statement did not specify the number of doses released, but in August the company confirmed that it planned to provide 250,000 doses in September and October for distribution in November.
In 2011 a trial involving more than 2,300 Flublok recipients found the vaccine's effectiveness to be 44.6% against all circulating strains in a season with significant antigenic mismatch between vaccine and circulating strains.
Nov 13 Protein Sciences press release
Jun 20 CIDRAP News story "ACIP recommends flu vaccine option for those with egg allergies"
Aug 5 CIDRAP News story on number of doses anticipated
Oct 13, 2011, Vaccine abstract detailing clinical trial