Key policy and programmatic factors to improve influenza vaccination rates based on the experience from four high-performing countries.

Background: Many countries consistently fail to achieve the target influenza vaccine coverage rate (VCR) of 75% for populations at risk of complications, recommended by the World Health Organization and European Council. We aimed to identify factors for achieving a high VCR in the scope of four benchmark countries with high influenza VCRs: Australia, Canada, UK and USA.

Methods: Publicly available evidence was first reviewed at a global level and then for each of the four countries.

Improving the selection and development of influenza vaccine viruses - Report of a WHO informal consultation on improving influenza vaccine virus selection, Hong Kong SAR, China, 18-20 November 2015.

Since 2010 the WHO has held a series of informal consultations to explore ways of improving the currently highly complex and time-pressured influenza vaccine virus selection and development process. In November 2015 experts from around the world met to review the current status of efforts in this field. Discussion topics included strengthening influenza surveillance activities to increase the availability of candidate vaccine viruses and improve the extent, timeliness and quality of surveillance data.

Influenza A (H1N1 09): public health lessons and questions.

Influenza A (H1N1 09) has been in Australia for 2 months and, in a world that had been preparing for a potentially dramatic outbreak due to H5 avian influenza, it has challenged global and national planning assumptions, definitions of pandemic influenza and our public health interventions. It has also highlighted how much we have yet to learn about both pandemic and seasonal influenza.

Influenza vaccine strain selection and recent studies on the global migration of seasonal influenza viruses.

Annual influenza epidemics in humans affect 5-15% of the population, causing an estimated half million deaths worldwide per year [Stohr K. Influenza-WHO cares. Lancet Infectious Diseases 2002;2(9):517].

Vaccines for pandemic influenza. The history of our current vaccines, their limitations and the requirements to deal with a pandemic threat.

Fears of a potential pandemic due to A(H5N1) viruses have focussed new attention on our current vaccines, their shortcomings, and concerns regarding global vaccine supply in a pandemic. The bulk of current vaccines are inactivated split virus vaccines produced from egg-grown virus and have only modest improvements compared with those first introduced over 60 years ago. Splitting, which was introduced some years ago to reduce reactogenicity, also reduces the immunogenicity of vaccines in immunologically naïve recipients.

The global circulation of seasonal influenza A (H3N2) viruses.

Antigenic and genetic analysis of the hemagglutinin of approximately 13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution.

The influenza viruses.

Human epidemic influenza is caused by influenza type A and B viruses, which continually undergo antigenic change in their surface antigens, haemagglutinin (H) and neuraminidase (N). Influenza epidemics are the consequence of small, ongoing antigenic changes known as "antigenic drift", which occurs in both influenza types. Pandemic influenza occurs at irregular and unpredictable intervals, and is the result of a major antigenic change known as "antigenic shift", which occurs only in influenza A.

Avian influenza: a pandemic waiting in the wings?

Recent widespread outbreaks of avian influenza and, associated with these a growing number of human infections with a high mortality rate, have raised concerns that this might be the prelude to a severe pandemic of human influenza. As a background to these concerns the present article reviews influenza as a human disease, its origins and the involvement of other species, properties of the influenza viruses and the current status of influenza prevention and control.

Geographic representativeness for sentinel influenza surveillance: implications for routine surveillance and pandemic preparedness.

Objective: To review the guidelines for geographic representativeness applied to sentinel influenza surveillance as proposed in the Framework for an Australian Influenza Pandemic Plan (1999).

Methods: The number of sentinel practices, participating general practitioners and their consultation rates per 100,000 population, by region, were described for the Victorian sentinel surveillance system for 2003 and 2004. Influenza-like illness rates per 1,000 consultations were calculated for all participating practices and for a subset of regular participators.

Report of the second meeting on the development of influenza vaccines that induce broad-spectrum and long-lasting immune responses, World Health Organization, Geneva, Switzerland, 6-7 December 2005.

New influenza vaccines that induce broad-spectrum and long-lasting immune responses and provide protection against divergent influenza viruses could overcome problems with the current vaccination strategy, based on annual intervention, better suit the needs of developing countries and contribute to epidemic and potential pandemic control. The World Health Organization held a consultation to review the current status of research in the area of influenza vaccines and to establish a research agenda for the development of such influenza vaccine. The main conclusions and recommendations from this consultation are presented below.

Detection of influenza viruses resistant to neuraminidase inhibitors in global surveillance during the first 3 years of their use.

Emergence of influenza viruses with reduced susceptibility to neuraminidase inhibitors (NAIs) develops at a low level following drug treatment, and person-to-person transmission of resistant virus has not been recognized to date. The Neuraminidase Inhibitor Susceptibility Network (NISN) was established to follow susceptibility of isolates and occurrence of NAI resistance at a population level in various parts of the world. Isolates from the WHO influenza collaborating centers were screened for susceptibilities to oseltamivir and zanamivir by a chemiluminescent enzyme inhibition assay, and those considered potentially resistant were analyzed by sequence analysis of the neuraminidase genes.

Neuraminidase inhibitor-resistant and -sensitive influenza B viruses isolated from an untreated human patient.

An influenza B virus from an infant with no history of treatment or contact with neuraminidase inhibitors demonstrated a significant reduction in sensitivity to these drugs. Here, we describe the analysis of a mixed viral population that contained a novel D197E amino acid substitution that was responsible for this reduction.

Neuraminidase inhibitor susceptibility network position statement: antiviral resistance in influenza A/H5N1 viruses.

The emerging epidemic of H5N1 avian influenza virus with spillover into the human population in Asia has provoked intense concern globally about the potential of these particularly pathogenic viruses to evolve with the capacity for human-to-human transmission with a consequent pandemic. The availability of antiviral drugs with activity against influenza A viruses and the recognition of drug-resistant variants to these drugs prompted the following report by a select group of the global experts--members of the Neuraminidase Inhibitor Susceptibility Network--on the best use of the available drugs, both for prophylaxis and treatment. The editors of Antiviral Therapy are pleased to be able to provide this document in an expeditious manner.

Reactogenicity and immunogenicity of an inactivated influenza vaccine administered by intramuscular or subcutaneous injection in elderly adults.

In many countries there is no clear recommendation regarding the preferred route of administration of inactivated influenza vaccines. In a randomised, observer blind study of 720 elderly subjects, a split, trivalent influenza vaccine was significantly more immunogenic for both A strains (H3N2 and H1N1, p = 0.0016 and 0.

A comparison of a rapid test for influenza with laboratory-based diagnosis in a paediatric population.

The rapid and accurate detection of influenza A and B in a hospital setting is useful to confirm infection, exclude other diseases and assist in the management of patient illness including the possible use of specific antiviral therapy. We evaluated the use of the Directigen Flu A+B in a paediatric hospital laboratory in comparison with the established diagnostic tests direct immunofluorescence, viral culture and reverse transcriptase-polymerase chain reaction. A total of 193 respiratory specimens were examined and the Directigen test detected positive samples with an 80.

Annual report of the National Influenza Surveillance Scheme, 2004.

The National Influenza Surveillance Scheme includes data on influenza-like illness from sentinel general practitioner practices, laboratory reports of influenza from National Notifiable Diseases Surveillance Scheme and absenteeism data from a national employer. In 2004, 2,116 cases of laboratory-confirmed influenza-like illness were reported, which was 41 per cent lower than the previous year. Peak activity was recorded in September, a month later than in 2003.

Concurrent summer influenza and pertussis outbreaks in a nursing home in Sydney, Australia.

Objective: To report on the investigation of a summer outbreak of acute respiratory illness among residents of a Sydney nursing home.

Design: An epidemiologic and microbiological investigation of the resident cohort at the time of the outbreak and medical record review 5 months later.

Setting: A nursing home located in Sydney, Australia, during February to July 1999.

Surveillance for neuraminidase inhibitor resistance in human influenza viruses from Australia.

Two hundred and forty-five human influenza A and B viruses isolated in Australia between 1996 and 2003 were tested for their sensitivity to the NA inhibitor drugs, zanamivir and oseltamivir using a fluorescence-based neuraminidase inhibition assay. Based on mean IC50 values, influenza A viruses (with neuraminidase subtypes N1 and N2) were more sensitive to both the NA inhibitors than were influenza B strains. Influenza A viruses with a N1 subtype and influenza B strains both demonstrated a greater sensitivity to zanamivir than to oseltamivir carboxylate, whereas influenza A strains with a N2 subtype were more susceptible to oseltamivir carboxylate.

Annual report of the National Influenza Surveillance Scheme, 2003.

Surveillance of influenza in Australia is based on laboratory isolation of influenza viruses, sentinel general-practitioner practices for influenza-like illness, and absenteeism data from a major national employer. In 2003, the peak in influenza activity was in August which was later than in 2002. In 2003, 3,604 laboratory-confirmed cases of influenza were notified to the National Notifiable Diseases Surveillance System, which was marginally lower than for the previous year.