Researchers find last year’s flu vaccine 39% effective
Leading US viral researchers assessed flu vaccine effectiveness (VE) against two viral strains during the 2019-20 flu season, finding 39% overall effectiveness. The study in Clinical Infectious Diseases late last week suggests that the seasonal flu vaccine was 45% effective against a mutated Victoria lineage B strain, but only 30% effective against 2009 H1N1 variants due to a late-season vaccine mismatch.
Flu viruses are prone to “antigenic drift”—mutations that produce novel strains to which people have little or no immunity—necessitating yearly reformulation of vaccines. Scientists rely on year-round surveillance to predict which strains will predominate, resulting in occasional mismatches between circulating viruses and those targeted by seasonal vaccines, and suboptimal vaccine effectiveness.
Researchers with the Centers for Disease Control and Prevention (CDC) and other national research institutes noted the emergence of two antigenically drifted flu strain lineages at the start of the 2019-20 flu season—B/Victoria and 2009 H1N1. They studied 2,722 patients aged 6 months and older at five national sites who tested positive for any type of influenza by RT-PCR. The study authors assessed VE for each viral sub-type by comparing odds of vaccination in flu patients versus non-flu control patients.
From Oct 29 to Dec 31, 2019, B/Victoria viruses accounted for 77% of flu cases. From Jan 1 to Mar 26, 2020, 58% of flu cases were due to 2009 H1N1. Overall, 44% of patients tested positive for the B/Victoria flu strain (1,209 of 2,722) and 51% tested positive for 2009 H1N1 (1,405 of 2,722).
VE against any influenza illness was 39% (95% confidence interval [CI], 32% to 44%; P < 0.05), and consistent across age-groups. Overall VE was 45% VE for B/Victoria viruses (95% CI, 37% to 52%) and 30% against 2009 H1N1 (95% CI, 21% to 39%). Vaccination provided no protection against variants of the 2009 H1N1 strain that predominated after January.
“This highlights the challenges in predicting vaccine protection against drifted influenza viruses,” the study authors wrote. “Even in seasons when circulating viruses are antigenically drifted from the vaccine virus, vaccination can provide protection.
“Preventing ~40% of any influenza-associated illness through vaccination in [the] 2019-2020 influenza season was particularly encouraging in the context of influenza virus infections causing an estimated 4.3-21 million outpatient visits, 140,000-810,000 hospitalizations, and 12,000-61,000 deaths annually in the US,” the authors wrote.
Dec 25 Clin Infect Dis study
Avian flu outbreaks strike more birds in Europe, Israel
More countries reported highly pathogenic avian influenza outbreaks in poultry and wild birds over the holiday period, according to the latest notifications from the World Organization for Animal Health (OIE).
Ukraine officials reported an H5 outbreak at a village in Kiev oblast that started on Dec 23 killing all 463 susceptible birds. They also reported an H5 detection on Dec 26 in a backyard bird in the same oblast, as well as a similar outbreak in backyard birds in Nikolayev oblast that began on Dec 23 killing 3 of 21 birds.
Elsewhere in Europe, a handful of other countries reported more H5N8 outbreaks. France reported an event at a farm in Hautes-Pyrenees department that began on Dec 19 killing 146 of 700 birds. Germany reported more outbreaks in two different states, one at a goose breeding farm in Saxony state that began on Dec 24 killing 75 of 9,000 birds and one at a turkey farm in Lower Saxony state that began on Dec 23 killing 14 of 13,000 birds. Also, Poland reported three more outbreaks, one at a turkey farm in Warminsko-Mazurskie province, one at a noncommercial chicken farm in Dolnoslaskie province, and one at a commercial turkey farm in Wielkopolskie province.
Elsewhere, Israel reported another H5N8 outbreak, which began on Dec 11 striking a commercial turkey farm in Jerusalem, where the virus killed 500 of 18,500 birds.
Also, several countries in Europe reported more detections in wild birds.
Dec 24 OIE report on H5 in Ukraine
Dec 28 OIE report on H5 in Ukraine
Dec 28 OIE report on H5 in Ukraine
Dec 24 OIE report on H5N8 in France
Dec 25 OIE report on H5N8 in Germany’s Saxony state
Dec 25 OIE report on H5N8 in Germany’s Lower Saxony state
Dec 28 OIE report on H5N8 in Polish turkeys
Dec 28 OIE report on H5N8 in Polish chicken and turkeys
Dec 28 OIE report on H5N8 in Israel
OIE avian flu outbreak page