Influenza season is almost here and vaccination is recommended for everyone over six months old.In New Zealand, five vaccines are available.Whether you're eligible for a free shot or having to pay for it yourself, it's worth considering your options.Why are flu shots updated annually?Each year, experts monitor influenza patterns and try to predict how the viruses might mutate.Based on these predictions, vaccines are updated to provide protection from the dominant strains.New Zealand's flu season typically runs from May to October, with the immunisation programme running from 1 April to 31 December.In 2025, the southern hemisphere vaccines are quadrivalent vaccines, with two influenza A strains and two influenza B strains.The five available in New Zealand are Influvac Tetra, Flucelvax Quad, Fluad Quad, FluQuadri, and Afluria Quad.Drug-buying agency Pharmac is responsible for setting the eligibility criteria for funded influenza vaccines. This year, Influvac Tetra is the funded vaccine.Four other, unfunded vaccines are available.Some people may have free access to them through their workplace.Having options is normal, but "the number and types of vaccines have expanded in recent years", Wellington doctor and Immunisation Advisory Centre medical director Nikki Turner told RNZ.What vaccine should I get?All vaccines are protein-based, meaning they're not "live" and cannot cause influenza, Turner said. They all target similar strains.Fluad Quad's point of difference is that it's targeted for people aged over 65."It's got what's called an adjuvant in it," Turner explained. "That's something extra to make a more vigorous immune response."While younger immune systems tend to respond "very well" to traditional flu vaccines, "as you get older, your immune system doesn't respond quite as well".This means the flu is more dangerous for older adults, with research suggesting people aged 65-plus account for up to 80 percent of influenza-related deaths and 70 percent of hospitalisations."There's probably an advantage with the adjuvanted one for frail, elderly patients."Exactly how big an advantage is hard to say, as data comes from observational studies, rather than clinical trials.Flucelvax Quad's point of difference is that it's cell-based, rather than egg-based.Since the 1950s, the most common way flu vaccines are made is by growing the virus in embryonated chicken eggs.When the United States experienced an egg shortage recently, with avian influenza partly to blame, the appeal of alternative vaccine-manufacturing processes became clear.Cell-based vaccines - grown in mammalian cells instead of eggs - are the way of the future, according to Turner.Are they more effective?Again, no randomised trials compare the efficacy of egg-based and cell-based vaccines, but some studies have shown the latter to be slightly better at preventing illness.Who's eligible for a free shot?Adults are recommended to get a flu vaccine every year to protect themselves and reduce the spread of the virus.In New Zealand, the 2025 flu vaccine is funded for everyone aged 65-plus and for those most at risk of becoming very sick, such as those with long-term health conditions, reduced immune function, and pregnant people.Non-funded flu vaccines are available for purchase at medical centres and pharmacies, with most priced between $25-65. It can be worth shopping around.Fewer children funded for flu shotsHealth New Zealand recommends annual vaccination for children from the age of six months.During the 2022 season, Pharmac funded flu vaccines for all children aged 3-12, but in 2023, this was extended to start at six months of age.Since then, funding has been reduced.In 2025, children aged four and under, who have been hospitalised for respiratory illness or have a history of significant respiratory illness, can get a free shot.Professor and head of department at Otago University's Department of Obstetrics, Gynaecology and Women's Health, Peter McIntyre, said young children "have a relatively high burden of hospitalisation due to influenza".Last year, McIntyre and colleagues published research showing universal funding led to "substantially higher" rates of vaccination among children."Focusing flu vaccination funding only on those at the highest risk is a step backwards for New Zealand and will likely reduce uptake."Australia's Pharmac equivalent has funded flu vaccines for children aged between six months and five years since 2019.How well do flu shots work?How well an influenza vaccine works depends on several factors, such as the age and health of the patient, along with the match between the vaccine and the virus strains in circulation.In healthy adults, data collated by Te Whatu Ora suggests the level of protection against confirmed influenza is between 59-66 percent."When you look at the numbers, they're not dream vaccines," epidemiologist Professor Michael Baker said.(By comparison, measles vaccines are about 95 percent effective after one dose and 99 percent effective after two, and that immunity is expected to last a lifetime.)Vaccines for respiratory infections, such as Covid and influenza, are good at protecting against "severe disease", but "not as effective as we'd like at stopping the virus from entering".While work is progressing in this area, in the meantime, "any vaccine is better than no vaccine".When should I get my vaccine?"Get it as early [in the season] as you can," Baker told RNZ.People tend to underestimate the flu, but it causes about 500 deaths a year in New Zealand, he said.Even months after an infection, an individual can be predisposed to a higher risk of heart attacks and strokes.Know something local worth sharing?Send it to [email protected] — we’ll help spread the word.