Mid-season additions to flu vaccinations?

[berkeman]

As you know, the flu vaccine this season is not doing so well:

https://www.cdc.gov/flu/professionals/vaccination/effectiveness-studies.htm

https://www.cdc.gov/flu/about/season/flu-season-2017-2018.htm

https://www.cdc.gov/flu/protect/vaccine/quadrivalent.htm

Why was quadrivalent flu vaccine developed?
For years, flu vaccines were designed to protect against three different flu viruses (trivalent). Trivalent vaccines include an influenza A (H1N1) virus, an influenza A (H3N2) virus and one influenza B virus. Experts had to choose one B virus, even though there are two different lineages of B viruses that both circulate during most seasons. This meant the vaccine did not protect against the group of B viruses not included in the vaccine. Adding another B virus to the vaccine aims to give broader protection against circulating flu viruses.

I thought the problematic strain this year is reported as the H3N2 virus, but the quote above implies that was included in the quadrivalent vaccine. Why can't they offer an additional vaccine to address the strain that is causing the low effectiveness of the vaccine? Does it take too long to culture and produce the vaccine?

 

[.Scott]

H2N2 is a virus subtype, not a specific virus.
https://en.wikipedia.org/wiki/Influenza_A_virus_subtype_H3N2

A vaccine for H3N2 will only protect against the targeted parts of a particular H3N2 - and any other viruses that happen to share those parts.

Of course, over the months it takes to develop and deploy the vaccine, the target pieces can change as the virus mutates. That can leave the vaccine less effective than hoped.

 

[Ygggdrasil]

It takes approximately five to six months for the first supplies of approved vaccine to become available once a new strain of influenza virus with pandemic potential is identified and isolated.

http://www.who.int/csr/disease/swineflu/notes/h1n1_vaccine_20090806/en/

(note: this page is from 2009, so more recent technologies, like cell based or recombinant methods, may have shortened the timespan. However, the page also refers to cases of flu with pandemic potential and not the annual flu vaccine, so it probably represents the fastest possible response with less regard to cost)

 

[BillTre]

Not all influenza symptoms are due to the flu virus.
This wikipedia article says the percentage of those with sympotoms having the Flu virus can vary from 14-70.

 

[.Scott]

More info here:
http://www.cidrap.umn.edu/news-perspective/2008/04/study-new-seasonal-flu-strains-launch-asia

 

[CWatters]

Here in the UK the issue last year seemed to be that the vaccine didn't protect the elderly as well as it did other age groups.

 

[Laroxe]

The people responsible for vaccines are also very interested in the problems of H3N2 vaccination, these are the things they have identified as important.

The seasonal epidemics usually involve a number of different flu viruses occurring at different frequency. Type A viruses tend to cause a more sever illness than type B. The type A virus H3N2 is known to cause a disease associated with more complications and it is the complications that generally cause serious illness and deaths. Quite naturally the different strains tend to result in antibody responses that are more or less effective in preventing further disease, in general terms vaccines that target Type A, H1N1 appear around 75% effective, Type B viruses around 54% and the type A H3N2 around 33%. These are population averages but are highly variable, age is a major factor. These differences are magnified in the groups most likely to have a poor vaccine response. In the case of H3N2 the elderly are particularly at risk of a poor response.

Vaccines use example viruses a subtype of a particular strain often named based on where these viruses were collected. The current H3N2 virus used in the vaccine is the B/Victoria lineage, the closer the circulating virus is to the lineage used the more effective it is, however the H3N2 virus seems to mutate at a higher rate than other flu viruses and in areas that effect immunogenicity. The current virus circulating in the US appears to be of a different lineage, the strain was around last year and the year before in the US before Australia was hit hard.

One of the most popular theories relate to vaccine production, H3N2 is harder to grow in eggs, and it may be that the adaptation to growing in eggs may may induce the changes that reduce vaccine effectiveness.
In fact these problems were foreseen based on the Australian experience and there are already available some potential fixes. There are two products available specifically for use in the elderly, one gives a higher dose another uses an adjuvant to try and increase the response rate, these as yet haven't been evaluated. There is already a move towards producing a vaccine using recombinant technology which eliminates the need for growing the virus in eggs as well as being quicker. The quadrivalent vaccine extends the range of viruses covered and there is a huge research effort trying to produce a vaccine which targets parts of the virus that are common to the whole family of flu viruses and give a more enduring immunity.