Meta-analysis finds no negative impact of repeated flu vaccination
In a study designed to help clinicians and health policy makers decide whether to recommend and offer annual flu vaccination, a new meta-analysis published today found no evidence that prior season immunization blunts the protection of the current seasonal vaccine.
Researchers from Ontario and Hong Kong published their meta-analysis of observational studies today in BMC Medicine.
Some recent studies have raised the possibility that repeated flu vaccination might negatively impact protection.
From a literature search, 27 studies met the inclusion criteria for analysis, and they included 20 in their meta-analysis. The team compared vaccine effectiveness in four groups: those vaccinated in the current season only, those immunized in the prior season only, those in both seasons, and those in neither season.
Authors of the new meta-analysis found that regardless of previous season vaccination status, current season vaccination was associated with greater protection against lab-confirmed H1N1 and influenza B infection. When compared to those who weren't immunized the season before, people who were vaccinated in the current season had greater protection against all three flu subtypes. "Therefore, vaccination in the current season is generally the best option for the patient," they wrote.
The only exception they found was for the 2014-2015 season, in which pooled vaccine effectiveness across three of the studies was lower for those vaccinated in both the current and previous season compared to those who were only vaccinated during the current season. (The H3N2 component that year was a poor match with the circulating strain.)
Researchers said their findings were similar to a review in 1999, but that their review includes the latest lab-testing methods with study designs and offers more consistency across vaccination groups.
Aug 21 BMC Med abstract
H5N8 avian flu strikes again in 2 South African provinces
South Africa today reported two more highly pathogenic H5N8 outbreaks, including one in newly affected Kwazulu-Natal province in the southeast of the country, according to a report from the World Organization for Animal Health (OIE).
The virus was first detected in South African poultry in June, and H5N8 has now been detected in four provinces.
The latest outbreaks occurred in backyard birds in earlier-affected Mpumalanga province and a commercial farm in Kwazulu-Natal. The events began on Aug 11 and Aug 17, respectively, and between the two locations, the virus killed 93 of 248,266 susceptible birds. The remaining ones were culled as part of the outbreak response.
Aug 21 OIE report on H5N8 in South Africa
Australia, Southeast Asia among current global flu hot spots
High flu activity continues in parts of the Southern Hemisphere and in Southeast Asia, the World Health Organization (WHO) said today in its latest global flu update.
In Australia, flu is still rising, with differences among regions. New South Wales is reporting steep increases in flu-like illness and pneumonia hospitalization. In a separate Australian government flu surveillance report, officials said that, as of Aug 4, that there has been a nearly two-and-a-half-fold increase in the number of lab-confirmed flu infections compared with this time last year, fueled in part by an earlier onset of the season and the introduction of rapid testing.
H3N2 has been the dominant strain, and influenza B continues to circulate. Adults age 85 and older and young children ages 5 to 9 have been the hardest hit groups. So far seasonal flu vaccines seem to be a moderate-to-good match for the circulating viruses, the Australian health department report said.
In New Zealand, where H3N2 and influenza B are the predominant strains, flu activity is declining. Elsewhere in the Southern Hemisphere, flu is decreasing in South America and appears to have peaked in South Africa.
In Southeast Asia, flu activity continued to increase, with all subtypes reported for the region. Sharp increases were reported from Myanmar and the Philippines, especially involving 2009 H1N1, and in Thailand, where H3N2 is the dominant strain.
Other flu hot spots include South Asia, where increased 2009 H1N1 detections were reported from India and Nepal, and Southern China and Hong Kong, where activity seems to have peaked but is still elevated.
Globally, flu virus testing through Aug 6 found that 91% were influenza A and 9% were influenza B. Of the subtyped influenza A strains, 88% were H3N2.
Aug 21 WHO global flu update
Aug 4 Australia Department of Health flu surveillance report