Let’s talk about effectiveness

There’s an elephant in the room. The media is reporting that this year’s flu shot is only 10% effective, and that isn’t the news that we want to hear. Higher effectiveness means better prevention, fewer hospitalizations, and more lives saved, and 10% isn’t ideal.


While most reports are giving us this 10% figure and stopping there, there’s more information that often isn’t included in these stories, and we’re going to dig into those details today to help you have the healthiest possible flu season. The flu is preventable, but no one method is a 100% guarantee against contracting and spreading influenza. It takes a multi-faceted approach, and it takes all of us doing our part to keep ourselves and each other healthy. Let’s break this down.

1) That 10%. What is it referring to? 

This is important. Depending on which shot you received you’ve been vaccinated against either three or four strains. The trivalent contains two A strains (H3N2 and H1N1) and one B strain, while the quadrivalent includes those three as well as an additional B strain. The quadrivalent is especially important for seniors and young kids who suffer the effects of B strains much more seriously than healthy adults do, but A strains are the ones that are responsible for pandemics.

Our flu shot in North America contains the same components as the shot used in the southern hemisphere this past season, and if you’ve seen the reports you know that some countries, like Australia, were hit particularly hard by influenza, including H3N2, with more serious events this season than they’ve had before on record. Early reports are showing that the flu shot only provided 10% protection against this strain this season. Combined with low participation rates, H3N2 didn’t have many obstacles to slow its spread. It’s important to note, though, that the overall effectiveness of the flu shot this year in Australia was 33%, indicating that H1N1 and included B strains performed much better than the H3N2 component did. It’s also important to note that H3N2 is typically the hardest to match, and a ‘good’ match for that strain is around 35%.

The effectiveness rates for the same season and flu shot were 50% for H1N1 and 57% for influenza B. A universal flu vaccine is about a decade away, but until then our seasonal flu shots – while imperfect – reduce the flu rates significantly.

TAKEAWAY: Your flu shot contains three or four different strains, and one of those strains demonstrated lower than usual effectiveness in Australia. It is difficult to predict this early in the season how the other two or three strains will perform in our flu season, but it’s also difficult to predict how much protection we’ll get from the H3N2 component. 10% refers only to Australia’s numbers on one included strain, while reports are omitting the much better effectiveness of other included strains.

2) Why are we talking about one strain’s effectiveness?

Influenza is unpredictable. We can’t know from one season to the next, or one hemisphere’s season to the other’s, how any given strain can mutate and impact the populations. The flu is tricky and a team of experts tracks its patterns each year in an effort to pick vaccine strains with the best possible matches to the strains that are expected to be dominant. It’s impossible to know exactly how the strains will move and change, so it’s a matter of predicting based on the best available information.

In a flu season there are typically two peaks – A strains peak earlier, often around December or January, and B strains peak later, often in March or April. While any number of strains can circulate and affect people, they usually find that an A strain will gear up and crowd out others to become the predominant strain. This doesn’t mean that the other strains won’t play their part, it just means that more people will suffer from the predominant strain. H3N2 hit Australia hard through their flu season, during our summer months. There’s a question now about whether we’ll follow their lead, or if they’ve followed ours. H3N2 was the predominant strain in North American during the 2016/17 season, so while it’s possible that we’ll have another difficult season with it, it’s also possible that it will lose steam and we’ll have an H1N1 season. The fact is, it’s too early to tell for sure. Flu activity is rising, but it isn’t totally clear yet which strain will dominate.

TAKEAWAY: If H3N2 is the predominant strain, we’ll have modest protection from the shot this season. That’s important information so we can take extra care to prevent the spread of influenza, but it’s too early to know whether H3N2 will cause the bulk of cases this year.

3) Is there still value in getting the flu shot?

YES. While it might only offer modest protection against the H3N2 strain, there’s more to the vaccine than that strain.

  • The flu shot still protects against 2-3 other strains (depending on which version you received). We don’t know yet how effective they’ll be, but they’re anticipated to be reasonably good. This protection is especially important for higher risk individuals (kids under 5, adults over 65, pregnant women, and people with underlying health conditions like asthma, cancer, and heart disease). It’s just as important for people who are in contact with higher risk individuals to take whatever preventative measures possible.
  • H1N1 may still become the predominant A strain. Getting the shot will help protect you from contracting and spreading what might still be the biggest concern this season.
  • B strains, which typically peak in the spring, are already showing increased activity much earlier than usual. We don’t know yet which B strains will be most problematic, but B strains lead to much higher numbers of lives lost in our youngest and oldest groups and we can protect these groups by participating in annual vaccination.

TAKEAWAY: This year’s shot might not give as much protection against H3N2 as we’d hope, but it may offer some protection against H3N2, as well as better protection against the other included strains. Some protection is always better than none, and we won’t know until later in the season how effective it might be against the viruses circulating here. Over the past four years in North America we’ve seen alternating seasons between H3N2 and H1N1. While some early numbers suggest H3N2 could be problematic this year, in the 2015/16 season we saw a similar pattern where it looked like H3N2 was gaining steam, and instead H1N1 took over. It’s just too early to be sure. If you’re reconsidering getting the shot because of lower H3N2 effectiveness, consider also the included H1N1 and B strains which performed significantly better in Australia this year. If we’re having an H1N1 or B season, you’ll want the protection.

4) Why might the H3N2 component not be as effective this year?

Good question! One of the answers might be in the process used to make flu vaccines. As we know, the flu is unstable and mutates very quickly. So quickly, in fact, that it’s possible for it to mutate as it’s being grown for production. While they’re working on new methods for growth, at this point the standard process is for the virus to be grown in eggs. This step provides an opportunity for the virus to mutate, which can make it a poorer match for the virus in circulation. This makes it harder for the protection our bodies makes against the H3N2 contained in the vaccine to recognize H3N2 if we contract it than it would be if the component in the shot looked more like the virus going around.

5) What other measures can we take in a lower effectiveness year?

This one’s easy, because these are measures we all should take each year, whether we get the flu shot or not. But these do become more important in a year when effectiveness for one or multiple strains is lower, and when participation might be lower.

  • Practice frequent handwashing – at least eight times a day – and avoid touching your face.
  • Cover your coughs and sneezes. The flu and can spread up to 6′ away.
  • Stay home if you’re sick. Going in to the office with a fever won’t make you a hero, and by taking your illness with you there’s a chance you’ll spread it to someone who might not be able to recover. Stay home until you’re well. Your coworkers don’t want what you have.
  • Keep sick kids home from school. One sick kid with a fever can quickly turn into 20 kids with the flu, who can pass it on to everyone they have at home. Kids are wonderful, but they’re also germy. If your child is showing flu-like symptoms, keep them home until they’re a minimum of 24 hours symptom-free without medication. Your school or daycare might have different rules, so check your handbook.
  • If you’re sick and you have plans, let the people you’re meeting know ahead of time so they can make a decision about their own risk.
  • Get plenty of rest, eat well, and exercise.

6) Is there anything else we can do to manage through this season?

Yes! Especially if you’re in a higher risk group. If you’re under five, over 65, pregnant, or have an underlying health condition, and you start showing flu-like symptoms while the flu is in circulation, see a health care provider immediately for antiviral medication. While it can’t kill the flu, it can stop its growth and give you the chance to avoid more serious complications, as well as recover more quickly than you would without intervention. See this fact sheet from Public Health Ontario for more information about antiviral medications.

IN CONCLUSION: Australia’s reports about the H3N2 component aren’t ideal, but we won’t have any information until February’s interim reports about how the same component will do in our own season. We can hope that it’s better than 10%, but if the number holds steady that’s still 10% fewer vaccinated people contracting the flu and being at risk for its serious complications. We don’t know yet which strain will be dominant, but if it’s an H1N1 or B season and Australia’s numbers are accurate for us, there’s much better protection against these strains in the shot. If you haven’t had your shot yet, don’t let one part of a bigger report put you off. The flu shot is still your best first defense against contracting and spreading the flu. Get your shot if you’re medically able, and take all possible prevention methods seriously in addition to your shot. Not only might you be saving yourself the misery of influenza, you might also be saving someone’s life.

Don’t let perfect be the enemy of good. We don’t yet have universal protection against influenza, but it’s in the works, and it’s going to save a lot of lives. I wish we’d had it two years ago. In the meantime, we have an annual exercise in doing whatever we can to prevent the spread of the flu. Influenza is preventable, but only when we all do our part. Do your part. Help us protect each other.

If you have any questions, please reach out to your doctor for more information.

ON A PERSONAL NOTE: I can set myself aside in all of this and talk about the facts, the science, the bizarre unpredictability of this virus that turns in ways we can’t expect. But at the beginning of the day and the end of the day, and so many parts in between, it will always come back to Jude. I’m emailing doctors and having phone chats with influenza experts and talking to anyone who will listen because Jude isn’t here. I would trade everything I have in the world for my old life back, but I can’t have that.

Jude’s flu shot didn’t protect him. He was vaccinated in December and died in May. I wish the flu shot was more effective. I wish 100% of the people who received it were fully protected against his crazy virus that’s far more serious than any of our casual conversations about it might have people believe. When you tell me that the flu shot isn’t a guarantee, you’re preaching to the choir.

But the only peace I’ve had since learning Jude’s cause of death comes from the knowledge that we did everything in our ability to protect him, and this happened despite our best efforts. I don’t know how I’d ever sleep again if we’d skipped flu shots that year. I’m not sure how I’d ever forgive myself for it, knowing that while the shot isn’t 100% effective, it’s better than nothing. It didn’t save Jude, but it saved a lot of people that year and every year.


Thank you to Dr. Dan Ricciuto and Dr. Janine McCready for helping me sort through the early part of these reports, and to Dr. Bryna Warshawsky who took the time to dig in deeper and proof this post. I’m not a doctor. While I’ve had a serious crash course in influenza over the last 16 months, this is a complicated disease and I know how tricky it can be for us to understand the way it moves and works. I’m grateful to all doctors and infectious disease experts who have helped me through this time so that I can communicate this message to you. As always, I recommend speaking with your doctor if you have any questions, and I hope that this site helps you as you make health choices for you, your family, and your community. 

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