Tag: mismatch

Will This Season’s Flu Shot Fail?

Flu season hasn’t even started yet, but we are all seeing anti-vax myths warning that the flu shot will fail in epidemic numbers. Where are they coming from?

Most of these anti-vax folks don't think that any vaccines work...
Most of these anti-vax folks don’t think that any vaccines work…

A lot of it is from the usual suspects…

Will This Season’s Flu Shot Fail?

Anyway, is there anything to this?

Can anyone really predict whether or not this season’s flu vaccine will be effective or if it will fail?

Probably not.

What they can do is scare folks into thinking that the flu vaccine won’t work, so that they don’t get vaccinated and protected, ensuring that we really will have a bad flu season!

Consider last fall. Many were predicting a mild flu season in North America following a mild season in the Southern Hemisphere and yet, 136 children died.

And this year?

Will a moderate to severe flu season in the Southern Hemisphere mean that we will be seeing a severe flu season too?

Maybe, but consider that the issue in the Southern Hemisphere wasn’t a vaccine mismatch.

Last year's flu vaccine in Australia was a good match.

They had a good match with their flu vaccine. The problem was just that they had a lot of flu!

So why do folks think that we will have a mismatch?

The A strains in the southern and northern hemisphere flu vaccines are different.

It’s because the A strains in the Southern and Northern Hemisphere flu vaccines are different, which is a little unusual, but not unheard of.

“Additional data obtained in recent weeks has confirmed the wide regional differences in the relative proportion of A(H3N2) viruses belonging to the phylogenetic subclade 3C.2a1b and clade 3C.3a. The majority of A(H3N2) viruses collected and genetically characterised from September 2018 to February 2019 belonged to the phylogenetic subclade 3C.2a1b; however, the proportion of viruses falling into clade 3C.3a has increased substantially since November 2018 in several countries in western Europe, Israel and especially in the United States of America.”

A lot of work goes into figuring out which strains to include in each year’s flu vaccine and that got us to where we are now.

Unfortunately, a lot of different flu vaccine strains circulate each season, which is why some folks get sick even though they have been vaccinated.
Unfortunately, a lot of different flu vaccine strains circulate each season, which is why some folks get sick even though they have been vaccinated.

Did they make the right decision?

Is our flu vaccine a match?

Some folks are saying that since they changed it again, for next year’s southern hemisphere flu vaccine, then they must have messed up.

So which flu virus strains are circulating so far? Will it be the 3c3.A clade of H3N2 that is in our flu vaccine? Will it be an H1N1 virus?

Of course, it is too early to tell.

“A/H3N2 viruses continue to show substantial diversity in HA sequences with a deep split between 3c3.A and 3c2.A1b viruses. The most notable recent developments are the rapid rise of clade A1b/137F – a subclade of A1b/135K – in China and Bangladesh and clade A1b/197R – a subclade of A1b/131K – which dominates the ongoing season in Australia. Our models predict that A1b/137F and A1b/197R will be the dominant clades next year with A1b/197R accounting for most circulation. There is, however, large uncertainty in the true extent of A1b/137F circulation.”

Bedford et al on Seasonal influenza circulation patterns and projections for September 2019 to September 2020

While we are seeing sporadic cases, flu activity is very low, which makes it a great time to get vaccinated and protected, before flu season really gets started.

And the predictions of a failed flu vaccine?

“Over the last 18 months, 3c3.A viruses have increased markedly in the US and Europe and accounted for 60% of isolates in North America and 10-20% in Europe during the last NH winter.”

Bedford et al on Seasonal influenza circulation patterns and projections for September 2019 to September 2020

I won’t let it get in my way of getting my family vaccinated and protected.

I’ll be getting my flu vaccine, crossing my fingers that they are wrong, and hoping that a universal flu vaccine gets here much sooner than later.

Even if they are right and one strain is mismatched, I understand that being vaccinated is the best protection against the flu and still provides many benefits, including the chance for milder symptoms and less severe disease.

And I know that the only true fail here, in addition to pushing misinformation about flu vaccines, is in skipping a yearly flu vaccine.

More on This Season’s Flu Shot

Is This Year’s Flu Vaccine Working?

Breaking News – Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness have now been released (see below)

Flu season is just getting started, but I’m sure that you have already heard folks rating how well this year’s flu shots are working.

Are flu vaccines working well?
Are flu vaccines working well?

Of course, if you had a flu shot and have already gotten the flu, then you’re gonna think the flu shot isn’t working very well at all.

And if you are vaccinated and protected and have avoided the flu, then it is working so far, right?

Is This Year’s Flu Vaccine Working?

While we won’t know how well this year’s flu vaccine is working until the CDC releases the preliminary estimates on flu vaccine effectiveness, there are some good signs already.

  1. The majority of the influenza viruses collected from the United States so far have been “characterized antigenically and genetically as being similar to the cell-grown reference viruses representing the 2018–2019 Northern Hemisphere influenza vaccine viruses.”
  2. The most frequently identified influenza virus type reported by public health laboratories was influenza A(H1N1)pdm09 virus.

Remember, to be effective, you want the flu vaccine to match the strains of flu virus that are circulating in the community. A mismatch in flu virus strain or antigenic drifting leads to lower flu vaccine effectiveness (VE).

Remember the 2004-05 flu season? That was the year that because of a drifted A(H3N2) virus, “only 5% of viruses from study participants were well matched to vaccine strains.” And the flu vaccine wasn’t very effective at all.

Still, even when the flu vaccine matches circulating strains, in general, as we have certainly seen, “flu vaccines provide better protection against influenza B or influenza A (H1N1) viruses than against influenza A (H3N2) viruses.”

YearFlu Virus StrainVE
2004-05A(H3N2)10
2005-06A(H3N2)21
2006-07A(H1N1)52
2007-08A(H3N2)37
2008-09A(H1N1)41
2009-10A(H1N1)pdm0956
2010-11A(H3N2)60
2011-12A(H3N2)47
2012-13A(H3N2)49
2013-14A(H1N1)pdm0952
2014-15A(H3N2)19
2015-16A(H1N1)pdm0948
2016-17A(H3N2)40
2017-18A(H3N2)40
2018-19A(H1N1)pdm0947

So if you had to guess, you could probably say that this year’s flu vaccine is going to be at least 50% effective.

So just as good as flipping a coin? Not exactly.

There are a lot of benefits to getting a flu shot besides avoiding the flu, like avoiding severe flu, hospitalization, and death.

And since flu vaccines are safe and flu can be a life-threatening disease, even in those without any medical problems, wouldn’t you take any chance you could to reduce your child’s chances of getting sick?

When will we know how well this year’s flu vaccine is really working?

The CDC typically releases the first preliminary flu vaccine effectiveness report of the season in February.

Not that you should wait! Flu season is well underway and this is a great time to get a flu vaccine and get protected for the rest of flu season.

Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness

On schedule, the CDC has released this year’s Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness.

During this period, overall adjusted vaccine effectiveness against all influenza virus infection associated with medically attended ARI was 47% (95% confidence interval [CI] = 34%–57%). For children aged 6 months–17 years, overall vaccine effectiveness was 61% (44%–73%).

Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness — United States, February 2019

That’s certainly better than we have seen in recent years.

More on the Effectiveness of This Year’s Flu Vaccine

Updated February 15, 2019