The data – yet to be published – is from the SHIVERS (Southern Hemisphere Influenza and Vaccine Effectiveness Research and Surveillance) study that tested a random sample of more than 2,500 Auckland people before, during and after the 2015 flu season.

The study found that 26 per cent of the participants were infected by influenza but only 20 per cent* had flu symptoms. Of those who had symptomatic infections, 77 per cent did not seek care.

The Immunisation Advisory Centre “strongly encourages” healthcare workers (HCW) to be vaccinated to protect both themselves and their patients as asymptomatic flu-infected HCW could unknowingly expose vulnerable patients to the virus. Last year 67 per cent of District Health Board nurses were vaccinated at work against the flu (see related story).

This year’s trivalent vaccine includes a new H1N1 virus strain – the first change to the H1N1 component of the vaccine since the virus caused the 2009 flu pandemic – and a H3N2 and B virus strain.

Another change in this year’s vaccine schedule is that people eligible for the funded influenza immunisation programme – pregnant women, people under 65 with certain medical conditions and people over 65 – will have access to the vaccine up until the end of December each year.

Pregnant woman and people over 65 are this year also eligible to go to approved pharmacies for their flu vaccinations.

*The SHIVERS serological survey included blood tests of the general practice patients before and after the flu season and weekly checks during the flu season to see whether people had cold or flu symptoms – and swabbing the nose or throats of those who did. Preliminary findings released by the ESR-led study on 20 September 2016 talked about 70 per cent of infected people not having flu symptoms, but this was updated to 80 per cent by researcher Dr Sue Huang in January 2017:


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