And know that until we get a better, universal flu vaccine, folks should know that talk about flu vaccine effectiveness is largely academic, as a yearly flu vaccine remains the best way to protect yourself from getting the flu and developing serious complications from the flu.
While we now think that flu vaccines are delayed if we don’t start seeing them in August, it is important to remember that it wasn’t that long ago that experts recommended that the optimal time to get a flu vaccination was in October and November.
It wasn’t until the 2006-07 flu season that we started to get updated guidelines for earlier flu vaccinations, starting with recommendations to offer flu shots in September for high risk groups “to avoid missed opportunities for vaccination.”
The next year the recommendation for the timing of flu vaccination became “health-care providers should begin offering vaccination soon after vaccine becomes available and if possible by October. To avoid missed opportunities for vaccination, providers should offer vaccination during routine health-care visits or during hospitalizations whenever vaccine is available.”
And with over 150 million doses of flu vaccine produced each year, it has been some time since we have seen a true flu vaccine shortage. The fact that more and more companies are making flu vaccines also helps ensure that shortages don’t happen.
Still, most flu vaccine manufacturers use older egg-based technology to grow flu virus strains for vaccine, which is not as reliable or flexible as many would wish it to be. This is what often leads to flu vaccine delays and shortages – the fact that in some years, the flu virus is simply hard to grow.
Flu Vaccine Delays and Shortages
How common are flu vaccine delays or shortages?
A flu vaccine delay and shortage in 2000 caused a supply of only 26.6 million doses of flu vaccine by October (vs about 76 million the previous year) and about 8 million fewer doses by the end of the season. The delay and shortage was caused by manufacturers having difficulty growing the H3N3 strain of flu and one fewer flu vaccine manufacturer.
In 2004, Chiron Corporation had its license suspended in the United Kingdom because of ‘concerns of possible microbial contamination of product.’ Chiron was to produce between 46-48 million doses of influenza vaccine for the United States and so overnight, we had our flu vaccine supply cut in half, leading to true shortages. An allocation plan that year helped to make sure that flu vaccine got to high-priority providers and people who needed them though.
In 2006, there was a delay in getting flu shots for younger children until November, as Sanofi Pasteur had difficulty producing their flu shots because of poor growth of one of the strains of influenza in the flu shot.
The emergence of H1N1 pandemic strain of influenza led to shortages in 2009. The problem that year was one of timing. The H1N1 flu virus was discovered just as seasonal flu vaccine was starting to be made, which led to a shift in priorities for flu vaccine production. The biggest problem, in addition to a slow growing H1N1 virus for the vaccine, was an early start to the flu season though. When H1N1 vaccine became available in October, it was too late for most people – flu season had already peaked.
After the 2009 H1N1 pandemic, we had several years of a more than ample supply of flu vaccine and on time delivery of our flu vaccine, which likely got most of us spoiled. It also was why we were all surprised by the production problems that led both GSK and Sanofi to have delays in shipping their flu vaccine in 2014.
We also had some flu vaccine delays in 2015. That year, MedImmune, the manufacturers of FluMist were supplying over 16 million doses of flu vaccine, but stated that “We expect customers will begin receiving product in early September and we will continue delivering vaccine throughout the season.”
Sanofi Pasteur also reported problems in 2015, stating that “Multidose vial orders are anticipated to be filled by the end of September; single use syringes will be supplied at a steady pace through November.”
2019-20 Flu Season Supply
Unfortunately, there will be some delays this flu season too, likely caused by a late update to the H3N2 strain because of drifting.
“Two strain changes coupled with the late decision for the H3N2 strain from VRBPAC, due to the drift that was being seen in surveillance was the issue. At least right now, capacity is all right with injectable vaccine.”
Remember, the WHO and FDA, via the Vaccines and Related Biological Products Advisory Committee (VRBPAC), made late decisions on which H3N2 strain to include in the 2019-20 flu vaccines.
So it shouldn’t be a surprise that pediatricians are getting notices that they will only receive a small part of their order of FluMist from AstraZeneca this year.
Or that Sanofi Pasteur, which will produce 40% of this year’s projected supply, is reporting a 4 to 6 week delay.
Even if word is just now trickling down to pediatricians, others have known about these delays for months…
Luckily, unlike delays in some other years, this doesn’t mean any shortages of flu vaccine. It is just that some doctors and clinics won’t be getting their first shipments as early as they would have liked. And not everyone will be able to get FluMist, if that is their preference.
Still, there will be a lot of flu vaccine and plenty of time to get everyone vaccinated and protected well before flu season hits!
What You Need to Know about Flu Vaccine Delays and Shortages
Other things to know about flu vaccine delays and shortages include that:
Pharmacies often seem to get their shipment of flu vaccine before pediatricians do, especially when there is any kind of delay.
Since even in a typical year, flu vaccine for the Vaccine for Children’s program gets to pediatricians a few weeks after other flu vaccine, this stock will likely also be delayed this year.
While they can certainly be frustrating, a flu vaccine delay shouldn’t mean that your family can’t get a flu vaccine.
Tamiflu can be an alternative to the flu shot for some high risk children who haven’t been vaccinated yet.
If there is a flu vaccine delay or shortage and your child is in a high risk group for complications from the flu, get a flu vaccine as soon as you can, wherever you can, and be sure you pediatrician puts you on a high priority list to get any vaccine that becomes available.
While H1N1 seems to be the most frequently identified influenza virus type this year, in reality, since causing the “swine flu” pandemic in 2009, this strain of flu virus never really went away.
It instead became a seasonal flu virus strains.
So it is back again this year, but just like it was back during the 2013-14 and 2015-16 flu seasons.
Is that good news or bad news?
In general, it’s good news, as “flu vaccines provide better protection against influenza B or influenza A (H1N1) viruses than against influenza A (H3N2) viruses.”
“The 2009 H1N1 influenza virus (referred to as “swine flu” early on) was first detected in people in the United States in April 2009. This virus was originally referred to as “swine flu” because laboratory testing showed that its gene segments were similar to influenza viruses that were most recently identified in and known to circulate among pigs. CDC believes that this virus resulted from reassortment, a process through which two or more influenza viruses can swap genetic information by infecting a single human or animal host. When reassortment does occur, the virus that emerges will have some gene segments from each of the infecting parent viruses and may have different characteristics than either of the parental viruses, just as children may exhibit unique characteristics that are like both of their parents. In this case, the reassortment appears most likely to have occurred between influenza viruses circulating in North American pig herds and among Eurasian pig herds. Reassortment of influenza viruses can result in abrupt, major changes in influenza viruses, also known as “antigenic shift.” When shift happens, most people have little or no protection against the new influenza virus that results.”
Origin of 2009 H1N1 Flu (Swine Flu): Questions and Answers
The only reason we were so concerned about this strain of H1N1 in 2009 was because it was new.
Still, even in a good year, it is important to remember that a lot of people die with the flu, including a lot of kids. And most of them are unvaccinated.
So while it might be interesting to talk about which flu virus strain is going around, just remember that your best protection against that strain is a yearly flu vaccine.
“The vaccine effectiveness of seasonal influenza vaccines is a measure of how well the seasonal influenza vaccine prevents influenza virus infection in the general population during a given influenza season.”
WHO on Vaccine effectiveness estimates for seasonal influenza vaccines
Is the flu virus that is going around the same strain that was picked to be in the flu vaccine?
Has the flu virus drifted, even if it is the same strain that is in the flu vaccine, becoming different enough that your protective flu antibodies won’t recognize it?
Is the H3N2 strain of flu virus the predominate strain during the flu season? H3N2 predominant flu seasons are thought to be worse than others.
In general, the flu vaccine is going to be less effective in a season where there is a poor match between the circulating strain of flu virus that is getting people sick and the strain that is in the flu vaccine, especially if it is an H3N2 strain that has drifted.
Unfortunately, we usually don’t know the answer to that last question until this year’s flu season really gets going.
What about reports that the flu vaccine effectiveness will be as low as 10% this year?
It is important to note that those reports are not based on flu activity in the United States and it has been a long time since we have seen flu vaccine effectiveness that low – 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.”
The 10% number is instead based on reports of Australia’s flu season, in which early estimates found that the A(H3N2) component of the flu vaccine was only 10% effective. Importantly, the overall vaccine effectiveness was much higher. Including other strains, the flu vaccine in Australia was at least 33% effective this past year.
“In the temperate regions of the Southern Hemisphere, influenza activity typically occurs during April – September.”
CDC on Influenza Prevention: Information for Travelers
Couldn’t we see a drifted A(H3N2) virus this year?
Sure, especially since an A(H3N2) virus will likely be the dominant strain, but so far “data indicate that currently circulating viruses have not undergone significant antigenic drift.”
“It is difficult to predict which influenza viruses will predominate in the 2017–18 influenza season; however, in recent past seasons in which A(H3N2) viruses predominated, hospitalizations and deaths were more common, and the effectiveness of the vaccine was lower.”
CDC on Update: Influenza Activity — United States, October 1–November 25, 2017
Again, it is too early to predict how effective the flu vaccine will be, but based on an undrifted H3N2 virus that is matched to the vaccine, you might expect an effectiveness between 30 to 40%.
It might be less if theories about egg-adapted mutations are true and are a factor this year.
“…some currently circulating A(H3N2) viruses are less similar to egg-adapted viruses used for production of the majority of U.S. influenza vaccines.”
CDC on Update: Influenza Activity — United States, October 1–November 25, 2017
It is also important to keep in mind that vaccine effectiveness numbers from Australia and the United States don’t always match up.
For example, in 2009, Australia reported an interim flu vaccine effectiveness of just 9%, but in the United States, the flu vaccine ended up being 56% effective! On the other hand, in 2014, the flu vaccine worked fairly well in Australia, but vaccine effectiveness was found to be just 19% in the United States.
Vaccine Effectiveness by Year
What does all of this mean?
“This season’s flu vaccine includes the same H3N2 vaccine component as last season, and most circulating H3N2 viruses that have been tested in the United States this season are still similar to the H3N2 vaccine virus. Based on this data, CDC believes U.S. VE estimates from last season are likely to be a better predictor of the flu vaccine benefits to expect this season against circulating H3N2 viruses in the United States. This is assuming minimal change to circulating H3N2 viruses. However, because it is early in the season, CDC flu experts cannot predict which flu viruses will predominate. Estimates of the flu vaccine’s effectiveness against circulating flu viruses in the United States will be available later in the season.”
CDC on Frequently Asked Flu Questions 2017-2018 Influenza Season
The reports about what happened in Australia should not have made headlines beyond Australia.
Folks should have waited for the yearly report on flu vaccine effectiveness from the CDC, which usually comes out in the middle of February. This year, that report states that:
the overall adjusted vaccine effectiveness against influenza A and influenza B virus infection associated with medically attended acute respiratory illness was 36%
vaccine effectiveness was estimated to be 25% against illness caused by influenza A(H3N2) virus, 67% against A(H1N1)pdm09 viruses, and 42% against influenza B viruses
the flu vaccine offered statistically significant protection against medically attended influenza among adults aged 18–49 years with an adjusted vaccine effectiveness of 33%
What about kids?
“…among children aged 6 months through 8 years, the interim estimates against any influenza and A(H3N2) virus infection were higher; the risk for A(H3N2) associated medically-attended influenza illness was reduced by more than half (59%) among vaccinated children. Also, with interim VE estimates of 67% and 42% against influenza A(H1N1)pdm09 and B viruses, respectively, vaccination provided substantial protection against circulating A(H1N1)pdm09 viruses, as well as moderate protection against influenza B viruses predominantly belonging to the B/Yamagata lineage, the second influenza type B component included in quadrivalent vaccines.”
CDC on Interim Estimates of 2017–18 Seasonal Influenza Vaccine Effectiveness — United States, February 2018
So the flu vaccine ended up being a lot more effective than folks predicted, especially in younger, higher risk kids, although it is still far from perfect.
Unfortunately, this year’s flu vaccine was not effective at preventing medically-attended influenza illness (flu case that sends you to see a doctor) for the 9 to 17 year old age group for some reason. That’s still not a good reason to skip the flu vaccine if your child hasn’t had it though, as the flu vaccine might still work to help your child, even if doesn’t fully prevent a case of the flu.
And while it isn’t perfect, getting a flu vaccine is certainly better than remaining unprotected and simply taking your chances that you won’t get the flu and complications from the flu.
What to Know About Flu Vaccine Effectiveness
Although the effectiveness of the flu vaccine varies from year to year, depending on how well matched the vaccine is to circulating flu virus strains, which strains are dominant, and whether they have drifted, it is always a good idea to get vaccinated and protected.