Are free flu shots targeted to the right people? School children, sometimes described as walking petri dishes, might be a double-whammy win for influenza reduction. 

As Australia suffers a terrible season of influenza which has already killed more than 100 people, news broke New Zealand has a vaccine shortage.

Last year 1.3 million doses of the influenza vaccine were distributed. Just a week into this year’s flu season and 1.26 million doses have been sold and national stocks are running low. Pharmac has said it’s unlikely more will be able to be sourced.

Health providers are now being asked to target the vaccines they have left to those most at risk.

These are pregnant women, the elderly, and those with chronic illnesses. For these people the vaccine is publicly funded.

To date, three Aucklanders have died from influenza: a 12-year-old, a 20-year-old and a 62-year-old, and there’s a spike in doctor visits of people suffering influenza symptoms. Annually it’s estimated influenza kills around 500 New Zealanders, either directly or from complications such as pneumonia, or respiratory or cardiac issues.

In the 2018 flu season the majority of people hospitalised were under 65. A third were hospitalised and half of those who ended up in intensive care had no pre-existing conditions.

The previous flu season was markedly different. The influenza virus strain circulating affected older people more. In 2017 it was mostly those over 65 and with pre-existing conditions who were hospitalised.

The current rate of GP visits for influenza like illnesses is higher than usual for this time of year. Source: Ministry of Health

Who responds best to the vaccine?

While a person over 65 might be most vulnerable to particular strains of influenza virus, there is a chance a vaccine won’t be as effective for them as it would be for a younger person.

As we age our immune system wanes. A 10-year-old’s body will often do a far better job developing antibodies to a virus than a 65-year-old’s body.

There’s a case to be made for immunising school-aged children to protect them as well as reduce the overall rate of influenza circulating.

University of Otago public health specialist professor Michael Baker said this is happening in some overseas countries such as the United Kingdom.

“That is a huge shift in thinking to a population protective effect.”

Unlike the measles vaccine, which is 97 percent effective, the yearly influenza vaccine varies in effectiveness. Influenza viruses have the ability to mutate. Each year vaccine makers try to stay one step ahead of the coming flu season and choose four strains most likely to circulate.

Sometimes this works well, other times it doesn’t. Effectiveness rates can vary between 30 and 65 percent. Traditionally this has meant individual protection has been the focus of vaccination programmes.

“With influenza, because the vaccine is still only moderately effective, the philosophy has been to give it to the most vulnerable. The next step in thinking is you also give it to people who spread it a lot, like little kids. Then you get a population protective effect and you’re dampening down transmission, the bonus effect of protecting the recipient, and reducing circulation,” said Baker.

In the United Kingdom, a study comparing the effectiveness of a nasal spray vaccine between pilot and non-pilot areas in 2015 showed vaccinating five- to 10-year-olds reduced GP hospital admissions for influenza in the vaccinated children by 93 percent.

There were also indirect effects on the wider community. Hospital admissions for influenza reduced by 61 percent in children under five, and there was a 34 percent reduction in admissions in people aged 17 and over.

Baker said a colleague who was an economist had completed a paper which mathematically modelled the impact that vaccinating school children in New Zealand would have. It’s awaiting publication.

“Generally, with vaccines, they’re almost always highly cost-effective because compared with the disease they’re cheap. That’s been a universal finding.”

Director of the Immunisation Advisory Centre Nikki Turner thinks having the vaccine is better than not having the vaccine, even if you are older.

“Your immune response might not be great, but you can still expect to get some. Anybody who is at high risk of the flu, for individual protection it’s still worth having the vaccine.”

She said a more effective strategy to control the spread of influenza might come from vaccinating people around vulnerable people. She also cited the UK example.

“It’s a different strategy, and it probably works better, but it’s in early days to see how that one goes.”

Adopting the United Kingdom’s approach would mean committing to an annual nation-wide vaccination scheme. The 2015 census put the number of children between five and 10 years old at 620,000.

This is similar to the number of vaccines currently administered to those Pharmac have currently identified as eligible for a free vaccine.

The vaccine shortage

Pharmac is responsible for purchasing flu vaccines for the country and works with the supplier to determine the number of doses needed for the following year.

The shortage is the second time in months there has been vaccine issues. In March, Christchurch ran low on measles vaccines in the middle of an outbreak.

Unlike measles, the influenza vaccine is reformulated each year based on predicted virus strains. There’s a lead time of several months to make the vaccine.

“Basically, they [Pharmac] predicted how many flu vaccines they need for the country and they didn’t get enough. The demand was higher than the predicted amount of doses,” said Turner.

“The world only makes so many flu vaccines per year based on how many they think they can sell. If you run out, you’ve run out. Suddenly you have a severe shortage of flu vaccines for the rest of the season.”

She said her message for next year is to order more doses.

“I would like to see us order more doses and not be constrained. I would rather we over-ordered than under-ordered them.”

Turner’s advice to those who have missed out on the vaccine this year and are not eligible for the remaining stocks is to stick to traditional approaches.

“When people are sick, they should stay home and not spread their bugs. Hand washing and hand sanitiser really, really work.”

Social distance is important too, she said.

“Do not cuddle young children and hang around frail elderly people when you are sick.”

Read more: 

Inside the flu’s spree of destruction

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