Lifestyle

The heart of the matter: how effective is the flu jab?

PEOPLE who think influenza vaccines are highly effective may have been surprised at recent news stories saying they're only moderately so.

Although vaccines are still the best tool available to combat this seasonal scourge, their ability to protect lies well below that of other vaccines, such as those given in childhood.

The inactivated influenza vaccine (flu jab) is the only one licensed for use in Australia.

To determine how well these vaccines protect people from the flu, scientists use results from two different types of studies.

The gold standard study is called a randomised controlled trial (RCT). The second type is the observational study.

>>More Health News

Randomised controlled trial

In an RCT, about half of the subjects get the vaccine and the other half receive a placebo (a shot that contains only saline or some other safe, inert material).

Those participating in the study don't know which one they've received until the study has concluded.

Researchers design the study so that people recruited to participate are very similar in terms of age, health status, and gender. I

t's important that both the groups are as alike as possible to ensure their bodies' response to the shots are directly comparable.

The design of randomised controlled trials also allows for more control over variables that can affect how well a vaccine works under ideal conditions.

Participants are checked each week to see if they have any symptoms of an influenza-like illness. If they do, they're tested.

This allows researchers to know with more certainty that they have tested everyone with symptoms in their study.

After a time, researchers determine the frequency of influenza in both groups and determine how well the vaccine works. This is called vaccine efficacy.

 

Observational studies

The most commonly used observational study is known as a case-control study.

This type of study helps estimate how well influenza vaccines work in a real-world setting, which is different to lab conditions for a number of reasons.

In a real-world setting, people unwell enough to seek out care and those with risk factors for complications become your primary study population.

This tends to reduce the impact of the vaccine when compared to RCTs (although improvements in study design have minimised this reduction significantly), but reflects how influenza vaccines are actually used.

With this study type, people seeking care for an acute respiratory illness (known as an influenza-like illness) at a doctor's office or medical clinic are voluntarily enrolled in the study.

They're identified as a case if they test positive for the influenza virus - meaning they were actually infected - and are designated a control if they test negative.

In the analysis, researchers compare the frequency of recent influenza vaccination among the cases and the controls, taking into account the same factors considered with the RCT.

This estimate of how well the vaccine protects is known as vaccine effectiveness.

 

So, how effective is it?

During the 2008 and 2009 influenza seasons, an RCT was conducted in Australia and New Zealand in healthy non-elderly adults.

Vaccine efficacy against all three influenza strains included in the vaccine was 60%.

Case-control studies conducted in Australia found similar results.

While the estimates of how well the vaccine works each year varies (because the formula of the vaccine changes), the average effectiveness from 2007 to 2011 was 62% in healthy adults under the age of 65.

How well the vaccine works in a given year also depends on the dominant strain of the virus in circulation and the population group that's most impacted by it.

All this means that, on average, healthy non-elderly adults in Australia can expect the vaccine to prevent an influenza infection serious enough to require medical care about 60% of the time.

Based on data from clinical trials, up to 10% of adults and up to 20% of young children will be diagnosed with seasonal influenza in a given year.

In children aged between six to 59 months, results from an observational study showed the vaccine works about 70% of the time in preventing influenza that requires medical attention.

Influenza vaccine efficacy and effectiveness studies including both observational and RCTs take place around the world.

The results of these Australian studies are similar to a recently conducted review of influenza vaccine efficacy and effectiveness from multiple countries.

 

The vulnerable

But data are limited on how well influenza vaccines work in adults over age 65 and in people with chronic health conditions and other risk factors that increase the likelihood of complications from influenza.

Yet these are the populations for which the influenza vaccine is strongly recommended and actively promoted in Australia and around the world.

What the data shows is that the influenza vaccine doesn't work as well in these populations as it does in healthy adults of working age.

Indeed, during the past influenza season, vaccine effectiveness in people over 65 in the United States was 27%, while overall effectiveness for all ages was 56%.

While influenza vaccines don't provide the level of protection desired by public health, they are still the best way to prevent influenza for most people.

They should continue to be used while better vaccines are developed.

 

>>Read more stories like this at The Conversation

Topics:  flu shots influenza vaccinations


Stay Connected

Update your news preferences and get the latest news delivered to your inbox.

What's causing CQ's heatwave

HEATWAVE: Temperatures will reach 41 degrees this week.

Temperatures will reach 40 degrees this week.

Baker backs 100% FIFO ban

Isaac Mayor Anne Baker

Mayor Anne Baker backs bill banning 100% FIFO workforces

Crews overcome challenges to deliver road project

Moisture check: Graeme Tuttle checking moisture consistency in all layers of stabilised pavement.

Isaac's essential agricultural corridor has received rehabilitation.

Local Partners

Come and celebrate Elmo's third birthday

Special Story Time sessions will be held in libraries across the region

Noll meltdown won't affect Gympie Oz Day concert

Shannon Noll

Photo Contributed

Shannon Noll is still expected to perform in Gympie next Thursday

Win your love with tickets

SMILES: Staff and children from Outside School Hours Care are fundraising for a new playground at the centre.

DAZZLE your darling with tickets to this year's Valentine's Day Ball

Be bowled over with fun at Australia Day

FACE OF REGION: Isaac Regional Council is proud to welcome world champion Brett Wilkie as the region's official Australia Day Ambassador for 2017.

Don't miss the Australia Day activities planned for the Isaac Region

Why Emma Watson turned down Cinderella

Emma Watson in a scene from the movie Beauty and the Beast.

HARRY Potter star has standards when it comes to Disney princesses.

Wonder Woman a ‘disjointed disaster’, says DC insider

Gal Gadot in a scene from the movie Wonder Woman.

INSIDER says the much-hyped blockbuster will disappoint.

Kid nails Swift impersonation

Seven-year-old Xia Vigor nails Taylor Swift impersonation on the Philippine talent show Your Face Sounds Familiar Kids.

TAYLOR Swift has a seven-year-old doppelganger.

Ariana Grande 'hardest working 23-year-old on Earth'?

Ariana Grande

Not everyone was impressed with Grande’s self-proclaimed work ethic

Why The Walking Dead cast are paid a pittance

Despite massive ratings the cast haven't been shown the money

50 Shades Dornan on why he hates the film

Dornan and Johnson’s frequent sex scenes were ‘awkward’ to film. Picture: SuppliedSource:Supplied

Jamie Dornan doesn’t blame you for hating 50 Shades

Sunday auction for historical home

Former Catholic school sure to attract spirited bidding

Looking back, looking ahead in Noosa

NEVER-ENDING GLORY: Looking towards Laguna Bay and Hastings St from Noosa National Park.

Natural appeal of Noosa continues to attract buyers

Thousands of jobs part of $1b retirement village project

THIS YEAR: An artist impression of the new Aveo retirement village in Springfield.

Aveo Springfield unveiled this month, homes ready by July

KNIFE-EDGE: The housing tightrope we now face

Even the smallest interest rate rise will be hard for some to handle.

One if five home owners at risk, according to new analysis

'Difficult times': Rental prices tipped to increase in 2017

GREAT BUYS: There are some great rentals and houses to buy in South Gladstone. Head to gladstoneobserver.com.au for the top 10 homes under $100 to rent right now in the Gladstone region.

Investors may soon see a "profitable return” on properties.

Ready to SELL your property?

Post Your Ad Here!