“Balancing considerations regarding the unpredictability of timing of onset of the influenza season and concerns that vaccine-induced immunity might wane over the course of a season, it is recommended that vaccination should be offered by the end of October.”
Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2019–20 Influenza Season
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.
“Influenza-like-illness levels have been elevated for 21 weeks this season, breaking the previous record of 20 weeks set during the 2014-2015 flu season.”
Situation Update: Summary of Weekly FluView Report Week 15
It’s likely that the media reports have been generated by a statement in the latest Weekly FluView Report that influenza-like-illness levels have been elevated for a little longer than usual this season.
What does that mean?
Well, influenza-like-illness levels are the proportion of outpatient visits for influenza-like illness (ILI), or basically, how many people are going to the doctor with flu symptoms. Once we get above the national baseline of 2.2%, we know that flu season has started.
“The proportion of outpatient visits for influenza-like illness (ILI) decreased to 2.4%, but remains above the national baseline of 2.2%. Seven of 10 regions reported ILI at or above their region-specific baseline level.”
Situation Update: Summary of Weekly FluView Report Week 15
And it ends when we get back below 2.2%.
What’s missing in the talk of the longest flu season, is that it doesn’t tell you much about the severity of the flu season. For example, the peak ILI this year was well below that of last year.
And flu season doesn’t start and end at the same time all over the country.
The bottom line? This has been an average flu season and a lot of people still died, including at least 91 children.
So whether it is a long or short flu season, severe or mild, get a flu vaccine and be protected.
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.