‘Tis the season to deck the halls with boxes of tissue. That’s right, guys. It’s flu season! Again.
Nobody wants to get the flu, but we can’t seem to agree on how to avoid it. Some people swear by the flu shot, others just can’t be bothered to get it, and many more are downright wary of it.
I spoke with Public Health Ontario physician, Dr. Bryna Warshawsky, to find out exactly how the flu shot works, who should get it, and why.
RK: How does the flu shot work?
BW: What happens is that in February the World Health Organization predicts what strains they anticipate will be circulating in the upcoming year and those strains are put into a vaccine. We offer a vaccine to adults that protects against three strains. Children between the age of six months to 17 years are given a vaccine that protects against four strains. The vaccine gives you a bit of the protein from the virus and your body makes an immune response or an antibody to that protein. If you are then exposed to the real virus, it activates the response before the virus takes hold and causes symptoms.
RK: Why does the flu shot seem to not work as well some years as others?
BW: The main reason is that the flu virus is constantly changing its proteins on the outside. We choose the vaccines for the upcoming year in February because it takes about six months for the vaccines to be developed. But in that six month period it is possible that the virus continues to change. So sometimes there’s not as good protection from the vaccine because the circulating strain has changed. On average, we know that the vaccine is about 50% to 60% effective and that it does vary from year to year. In general, it decreases your risk of getting influenza by about half. So it’s not the best vaccine we have, but if I said you had a 50% chance of winning the lotto you would think that was good. We know flu infects 5-10% of the population in any given year, so decreasing that by half is still a very substantial benefit.
RK: How dangerous is the flu?
BW: For healthy people, it’s a sudden onset of fever, headaches, sore throat, muscle pain and you feel quite ill and you need to go to bed. Generally, in a week you’ll feel better. The problem with influenza is two-pronged. One, is that it is spread widely. The other is that it can cause complications like ear infections, sinus infections, pneumonia, worsening of underlying medical conditions, as well as some unusual complications that can be fatal. These complications mostly occur in people who are elderly, pregnant women, young children under five (and especially under two), and people with other medical conditions. If you already have heart disease, lung disease, cancer, HIV, or you’re taking medications that affect your immune system, all of those will increase your risk for complications. So when we get vaccinated as healthy people it lowers our risk of getting sick by about 50% and it decreases our chance of spreading it to people who are at risk for complications. And, of course, those people being vaccinated as well further decreases their risks of getting the flu and getting complications.
RK: People always say things like, ‘I never get the flu, but the one year I went and got the shot, I wound up getting it.’ Is it true that the flu shot could make you more susceptible to catching the flu?
BW: No, you can’t get the flu from the flu shot and it doesn’t make you more susceptible to influenza. What happens, though, is that we get the flu shot around this time of year, right around October or November. This is a good time to get the shot; the right time. But there are other viruses circulating around. So if you pick up another virus after you’ve had your flu shot there’s a natural tendency to say that virus was related to my flu shot when it was just a coincidence. We know that viruses are circulating around this time of year that cause cold-like symptoms. The flu shot does not cause influenza, but it can make you feel achy and tired for a day or two, but that’s very mild and goes away.
RK: So the only side effects you should expect are achiness for a day or two?
BW: Sore arm is another common side effect. The other side effects can be a bit of a headache, sore muscles, or tiredness for a day or two, but generally very mild. Severe side effects such as Guillain-Barré syndrome are very rare.
RK: I don’t even know if I have the flu sometimes versus just a cold or a sore throat. Is there any way to know if you have the flu?
BW: It is hard in an individual person. Generally, flu comes on suddenly and causes a fever and a headache and you feel very tired. You feel very run down and you really have to go to bed. It’s still hard to distinguish that from any other virus. When flu is circulating, if you come down with those kinds of symptoms, it is more likely to be influenza. Doctors can test for flu with a swab, but we don’t generally do that unless a person is very sick.
RK: Is it important for everybody to get the flu shot? Or just for those more susceptible to complications?
BW: No, it’s really important for everybody. For healthy people it’s important because it will keep you healthy and at work or doing the things that you want to do. But it’s also important for healthy people because they can be the conduits for it to spread to other people who are at high risk. Certainly, healthcare workers being vaccinated is key, but even if you are not a healthcare worker, if you have children or someone with a medical condition at home, or you are visiting elderly parents or grandparents, you don’t want to be the source of influenza for them because they can get quite sick from it. They can end up hospitalized or with pneumonia, and, unfortunately, can end up dying.
RK: Because even if those people have gotten the shot themselves, it’s not 100% effective, right?
BW: Yes, if they have had the shot themselves, they have some protection. 50% is an average, but seniors tend to have lower rates of effectiveness from the vaccine. So if you can increase that protection by vaccinating the people they are in contact with, that decreases the chances that they will get flu.
RK: Is it ever too late in the season to get the shot?
BW: It’s not too late to get it even into the new year because flu can circulate sometimes into April and May, but it’s much better to get it early. This is the prime time to get it. It takes two weeks to mount an immune response and the flu can start to circulate as early as October. We’re already seeing a little bit of it. It can peak anytime over the next few weeks to months. There are also different types. So sometimes we see the A type come through in November to February and then after that we can see the B type happen a bit later. So it’s not too late to get it later on in the season, but you get maximal protection for yourself and those around you if you get it now before the flu season really takes off.
RK: For other vaccines, we talk about reaching a level of protection where there’s herd immunity for the general population. I guess with the flu virus, we can’t really hope for that same level of protection. The flu is still going to be circulating, no matter what, isn’t it?
BW: Yes, there’s no way we are going to be able to stop the flu from circulating. What we can do by being vaccinated is lower our chances by about 50% of getting infected and decrease the risk that we’ll spread it to other people. So it’s definitely a very good strategy for everybody to be vaccinated. It’s not perfect; we would hope that in the future we’ll have higher effectiveness. But 50% is still pretty good and it’s reducing your chances by half.
RK: Some people are worried that getting the shot year after year will overburden their immune system.
BW: Our immune systems are very robust and strong and can certainly accommodate vaccinations each year. There is some suggestion that perhaps if you’ve been vaccinated more often in the past, you might not get quite as much protection, but you certainly get way more protection than if you were not vaccinated. Even if you’ve had multiple vaccines in the past, your immune system is very strong and able to cope with that. And it’s still always better to be vaccinated in the current year than to rely on protection from the past years, so we do recommend vaccinations every year.
RK: Do some vaccines have a live virus?
BW: Yes. The FluMist that goes in your nose, which is one of the choices for children two to 17 years of age, has a live virus that grows in your nose and your throat. The live vaccine poses no risk for healthy people, so for healthy children, either the live nasal vaccine or the injectable one is a choice. They both offer broad protection against four strains of influenza. The only people who can’t get the FluMist are children who have underlying immune problems, children with bad asthma, and children on aspirin containing drugs. Otherwise, the vaccines are comparable.
RK: Does the mist not work for adults?
BW: It’s not the best choice for adults; it doesn’t work as well. Because adults have had lots of flus and infections before. In order for the FluMist to work, it needs to grow in your nose in to cause your immune system to respond as if it were flu. But because adults have lots of infections, they inactivate that vaccine before it has the opportunity to grow. The only reason we’d give it to an adult is if they were very afraid of needles and that was the only thing they would take.
RK: What if you are sick or run down? Should you not get the flu shot at that time?
BW: It’s still okay to get to the flu shot unless you are really sick with a severe and sudden onset illness; then you would wait. But if you just have a mild cold, then it’s still okay.
RK: And that applies to children too? My five-year-old will get a cold and her nose runs for weeks on end. I never know if she is better or not better.
BW: Yes, if you waited for her nose to stop running, you’d be delaying protection and she’d be at risk for getting influenza once it starts circulating. Certainly a runny nose or even a mild fever is not a reason to defer the shot.
The flu shot is widely available in doctors’ offices, public health clinics and drugstores across most of the country.
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