FLU NEWS SCAN: Healthcare H1N1 patterns, limited impact of H1N1 vaccine, H5N1 in Vietnam

Jul 18, 2011

H1N1 attack rate similar for clinic, nonclinical healthcare workers
In the largest known study of its kind, Hong Kong researchers reporting in Clinical Infectious Diseases found that attack rates of 2009 pandemic H1N1 influenza for clinical staff weren't different than for healthcare workers who didn't have direct patient contact. The study period covered the first 3 months of the pandemic, a time when all Hospital Authority workers were required to report all confirmed 2009 H1N1 infections. Of 1,158 confirmed cases during the pandemic, 368 occurred during this mandatory reporting period. The infection rate was 0.62% for clinical staff and 0.63% for nonclinical staff. Each infected employee completed a questionnaire designed to gauge exposure patterns. Twenty percent of each group reported that they had been recently exposed to a sick family member of friend. None of the nonclinical workers and 7.5% of the clinical employees said they had contact with sick patients. Nearly all clinical workers (96.6%) said they used a mask at all times, though the authors said participation and recall bias could have influenced the result.
Aug Clin Infect Dis abstract
In a related editorial in the same issue, infectious disease experts from Imperial College London wrote that one of the study's most interesting findings was that more healthcare workers reported they were more likely to be exposed to the 2009 H1N1 virus by an infected colleague or community member than a patient. They said that more researchers on infection patterns among healthcare workers is needed to help guide future workforce planning, epidemic response, and infection control strategies.
Aug Clin Infect Dis editorial extract

Study: Adjuvanted H1N1 pandemic vaccine had limited impact
A Dutch study published today in BMC Infectious Diseases concludes that the MF-59 adjuvanted vaccine for 2009 pandemic H1N1 flu "may have had only a limited impact" on preventing hospitalization in patients at high risk of complications and that a more effective vaccine or additional preventive measures are needed. Included in the study were 149 patients 60 years old or older with an underlying medical condition who were hospitalized with laboratory-confirmed H1N1 pandemic flu between Nov 16, 2009, and Jan 15, 2010, and 28,238 controls matched for age, sex, and type of underlying condition. An estimated 22% of cases and 28% of controls had been vaccinated more than 7 days before onset of symptoms. The authors state that "a considerable number of breakthrough infections" occurred. Vaccine effectiveness, termed "modest" by the researchers, was estimated at 19% (95% confidence interval [CI], 28%-49%). Vaccine effectiveness when analysis was restricted to controls with severe underlying medical conditions, as determined by number of prescribed drugs being taken, was 49% (95% CI, 16%-69%).
Jul 18 BMC Infect Dis abstract

H5N1 strikes two Vietnamese provinces
Vietnam's animal health ministry today said H5N1 avian influenza outbreaks in poultry have been detected in two provinces, Quang Tri on the north central coast and Phu Tho in northeastern Vietnam, according to a report today from the World Organization for Animal Health (OIE). The outbreaks sickened 3,704 birds in the two affected villages, and 3,704 more were destroyed to control the spread of the virus. Vietnam reported its last H5N1 outbreak in early June and is among the handful of countries where the disease is endemic in poultry.
Jul 18 OIE report

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