● Introduction [ver].
● Composition of flu vaccines in the northern hemisphere in the 2024-25 season [ver] | Reference documents | Recommended composition [ver] | Other documents [ver].
● Frequently asked questions, questions and answers from the WHO [ver].
● The preferential use of trivalent vaccines poses problems for vaccine manufacturers, regulatory agencies and Public Health authorities. [ver].
● More information on this website, references and recommended links [ver]. In a nutshell ● The WHO has published its recommendations for the composition of influenza vaccines in the northern hemisphere in the upcoming 2024-25 season.
● The WHO recommends preferably using trivalent vaccines, leaving aside the Yamagata lineage component of the influenza B virus.
● There have been no confirmed detections of B/Yamagata lineage influenza viruses since March 2020.
● The decision of the WHO, supported by the FDA, is a major commitment, facing great difficulties and public health challenges.
Introduction
Every year the WHO publishes its recommendations for the composition of influenza vaccines of the following season. In February for the northern hemisphere and in August or September for the southern hemisphere.
The recommendations are built from numerous sources of information: epidemiological surveillance of influenza, antigenic and genetic characterization of the detected viruses, serological studies, data on vaccine effectiveness, resistance to antivirals and others. This information is displayed on the website of the Global Influenza Surveillance and Response System (GISRS).
Following the deliberation of the expert groups convened by the WHO, the recommendations for the composition of influenza vaccines in the northern hemisphere in the next 2024-25 season, which are discussed below. The recommended composition of vaccines in the northern hemisphere in 2024-25 is the same as recommended for the southern hemisphere in 2024 (flu season from April to August 2024).
Composition of flu vaccines in the northern hemisphere in the 2024-25 season
Reference documents
In the next season, The WHO recommends using trivalent vaccinesleaving aside the Yamagata lineage component of the influenza B virus. No isolation of this virus has been confirmed since March 2020, so it is estimated that it is not necessary to include it.
Recommended composition
The WHO recommends that trivalent vaccines for use in the 2024-2025 Northern Hemisphere flu season contain the following (see image above):
- Egg-based vaccines:
- Un virus similar a A/Victoria/4897/2022 (H1N1)pdm09.
- Un virus similar al A/Thailand/8/2022 (H3N2).
- A virus similar to B/Austria/1359417/2021 (B/Victoria lineage).
- Vaccines based on cell cultures or recombinants:
- Un virus similar a A/Wisconsin/67/2022 (H1N1)pdm09.
- Un virus similar al A/Massachusetts/18/2022 (H3N2).
- A virus similar to B/Austria/1359417/2021 (B/Victoria lineage).
For the quadrivalent vaccinesin countries that decide to maintain them, based on eggs, cell cultures or recombinants, WHO recommends the inclusion of the following as a component of the B/Yamagata lineage: a virus similar to B/Phuket/3073/2013 (B/Yamagata lineage) .
The WHO points out that vaccines for the next season must contain viruses similar, from an antigenic point of view, to those mentioned as a reference. To do this, the WHO selects and authorizes a set of viral strains with similar hemagglutinin so that they can be used by different manufacturers.
Other documents
The WHO recommendations are accompanied by the following Additional documents:
Common questions, questions and answers from the WHO
Between the WHO answers to frequently asked questions the following are found.
How are WHO recommendations for the composition of influenza vaccines developed?
The WHO GISRS is made up of 151 influenza reference centers in 125 countries, 7 collaborating centers and 16 reference laboratories worldwide. The GISRS collects and analyzes data from different sources, such as those mentioned above, also including the availability of reference strains for vaccine manufacturing.
What does the expression “similar virus” mean in the composition of the vaccine?
The recommended vaccine viruses are representative of the antigenic group of viruses that are expected to circulate widely in the upcoming influenza season. Often, multiple candidate viral strains are available that possess HA antigens from other viruses that are antigenically similar to the recommended vaccine viruses. The term “similar virus” is included to allow the use of those other bioequivalent strains for vaccine manufacturing.
Have B/Yamagata lineage flu viruses become extinct?
There have been no WHO-confirmed detections of influenza viruses of the B/Yamagata lineage since March 2020. Recent reports of detections of B/Yamagata have not been confirmed or were identified as live attenuated vaccine viruses.
Although it cannot be certain that B/Yamagata lineage viruses are extinct, they are unlikely to cause outbreaks in the next season. On the other hand, there is a theoretical risk of dissemination associated with the use of this virus in the manufacture of inactivated or attenuated vaccines, which is why the WHO recommends that strains of this virus be excluded from the vaccines in use as soon as possible.
The preferential use of trivalent vaccines poses problems for vaccine manufacturers, regulatory agencies and public health authorities.
It might seem that returning to trivalent vaccines is a simple decision: “why vaccinate against something that does not exist”, “removing a component from vaccines is as simple as eliminating a component from a mixed fruit smoothie”, are arguments put forward. that reflect an approach that is too simple and far from complex reality. On the contrary, It is a decision that faces relevant difficulties and has very serious implications. that must be considered. It is not enough to say that “it is no longer necessary” to include the Yamagata component in vaccines, this being, to a large extent, true (Editorial, Lancet Infect Dis 2023; Wu KJ, The Atlantic 2024; Branswell H, STAT 2024).
Until 2012, only trivalent influenza vaccines (two influenza A virus components and one influenza B virus component) were used. The circulation of different variants of the influenza B virus led to the use of quadrivalent vaccines (two components of influenza A virus and another two of influenza B) in the 2013 season in the southern hemisphere. Since then, the use of these vaccines has only increased around the world (e.g., only quadrivalent vaccines have been used in the US since the 2021-22 campaign).
When, in September 2023, the WHO, in its recommendations for the 2024 influenza season in the southern hemisphere, again recommended trivalent vaccines (excluding the influenza B component of the Yamagata lineage), vaccine manufacturers stated that could have problems adapting their production systems in time to the regulatory requirements for the new trivalent vaccines (Express Pharma, October 2023). However, they were not the only difficulties raised, as they have also been raised in other areas.
At that time, a committee of experts who advise the US FDA (VRBPAC) was in complete agreement with the WHO and joined the recommendation to transition back to trivalent vaccines “as soon as possible” (Avalere, October 2023). However, they explained and debated that this decision faces various challenges in different fields (VRBPAC, FDA, October 5, 2023; Editorial, Lancet Infect Dis 2023; Wu KJ, The Atlantic 2024; Branswell H, STAT 2024):
- In the vaccine production, since they have to reactivate the vaccine manufacturing processes that had almost stopped being produced. It is estimated that this situation would affect more than 350 inactive licenses that would have to be updated (new potency studies, immunogenicity assays, etc.). Vaccine manufacturers (Seqirus, GSK, and the world’s leading manufacturer, Sanofi) have declared themselves “fully committed” to the WHO recommendations, although they have expressed that this will require some time.
- In the research into new vaccines, such as universal flu vaccines, mRNA vaccines, combined vaccines against covid and flu, etc., in development, which contemplated a horizon with the B virus of the Yamagata lineage. These investigations would have to be reoriented, dispensing with the Yamagata component, which is expensive and will delay the results.
- For the regulatory agencieswhich will have to evaluate, and where appropriate approve, new products, these procedures being extremely complex when they affect new products.
- And for the public health authorities, who will have to: a) decide the pace of the return to the preferential or exclusive use of trivalent vaccines according to their particular conditions; b) weigh the risks of keeping influenza B viruses of the Yamagata lineage in circulation in the production processes of inactivated vaccines and, above all, in the tetravalent attenuated vaccines that continue to be administered; c) assume the risk of the reappearance of this virus and the implications of the exclusive use of trivalent vaccines for population protection against a diversity of influenza viruses; and, among others, d) the need for a very rigorous global virological surveillance plan.
Consequently, it is expected that in the coming weeks (time is urgent, since having the vaccines available next fall takes time) the manufacturers, regulatory agencies and the experts and authorities involved will make the appropriate decisions to guide the deployment of the vaccines. new trivalent influenza vaccines, considering the general guidelines of the WHO and the particular conditions of each country. For its part, the US FDA has already announced that it will debate these issues as soon as Tuesday, March 5, this week.
-oOo-
More information on this website
References and recommended links
- Avalere, October 5, 2023. Influenza B Strain Removal Could Impact Future Flu Vaccines.
- Branswell H. The WHO and drug regulators want to reformulate the flu vaccine. It’s easier said than done. STAT, January 16, 2024.
- Express Pharma, October 25, 2023. WHO trivalent recommendations will reshape global flu vaccine market: GlobalData with recommendations for the northern hemisphere expected to follow suit.
- FDA, EE. UU. Vaccines and Related Biological Products Advisory Committee October 5, 2023 Meeting Announcement, october 5, 2023.
- Lancet, editorial. Influenza vaccine shake-up. Lancet Infect Dis. 2023;23(12):1323.
- WHO, February 23, 2024. Press release. Recommendations announced for influenza vaccine composition for the 2024-2025 northern hemisphere influenza season.
- WHO, February 23, 2024. Recommended composition of influenza virus vaccines for use in the 2024-2025 northern hemisphere influenza season. Detail of the recommendations. ►Commented on: CIDRAP, February 23, 2024.
- WHO, February 23, 2024. Questions and Answers. Recommended composition of influenza virus vaccines for use in the northern hemisphere 2024-2025 influenza season and development of candidate vaccine viruses for pandemic preparedness.
- WHO, February 2024. Genetic and antigenic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness.
- WHO, September 29, 2023. Recommended composition of influenza virus vaccines for use in the 2024 southern hemisphere influenza season. ►Commented on: CIDRAP, September 29, 2023.
- Wu KJ. Flu Shots Need to Stop Fighting ‘Something That Doesn’t Exist’. One type of flu virus has gone missing for so long, it doesn’t make sense to vaccinate against it. The Atlantic, February 5, 2024.
[volver al principio]
2024-03-04 06:11:37
#Composition #flu #vaccines #season