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H5N1 Avian Flu: Vaccination Strategy for Possible Cases in People in Contact with Infected Animals
Press release - Posted on Apr 08 2025
April 8, 2025 H5N1 avian influenza continues to spread worldwide, particularly in the United States, where it affects several animal species and causes infections in people in close contact with infected animals. To date, no human-to-human transmission has been observed. In response to a request from the Ministry of Health, the French National Authority for Health (HAS) has developed, in anticipation, recommendations on the vaccination strategy that should be adopted in the event of possible human cases exposed to infected animals in France. The HAS defines several scenarios and recommends vaccinating people exposed to the virus with the pre-pandemic vaccine from Seqirus, in the event of an increase in animal outbreaks and in the presence of severe human cases in contact with these outbreaks.
The highly pathogenic avian influenza virus H5N1 is responsible for the widespread global circulation of avian influenza in birds. Since 2021, the virus has also affected a wide range of mammals (terrestrial, marine). Infections in humans are rare and occur mainly after direct contact with infected animals: this is referred to as zoonotic influenza . As of March 12, 2025, US authorities have recorded 70 human cases of clade 2.3.4.4b avian influenza, since the first case reported in April 2024. Other human cases have been identified worldwide, including one in Europe in early 2025, in the United Kingdom.
The objective of vaccination is primarily to prevent the development of severe forms in the event of contamination and, potentially, to reduce the risk of contamination of humans by animals. The Zoonotic Influenza Vaccine (H5N8) from Seqirus is the only pre-pandemic vaccine with marketing authorization in Europe. It is an inactivated vaccine with an adjuvant, which induces a cross-immune response against H5N1 strains circulating in the world. Although it remains impossible, at this stage, to accurately predict the evolution of the virus, the Ministry of Health has asked the HAS to develop recommendations in advance on the vaccination strategy in the event of the detection of a human case of zoonotic influenza in the territory, whether indigenous or imported . The HAS has thus defined several scenarios, the priority population groups and specified in which situation vaccination with the Seqirus vaccine is recommended. To this end, it has taken into consideration the latest epidemiological data, the availability of the vaccine and its data (immunogenicity, efficacy and tolerance), the opinion of experts interviewed as well as the vaccination recommendations issued internationally.
The HAS specifies that these recommendations do not address a pandemic situation resulting from the virus's ability to transmit from human to human.
Vaccination recommended in the event of a significant increase in animal outbreaks and severe human cases
The detection of a single human case of avian influenza in the territory, whether indigenous or imported, does not justify the implementation of pre-pandemic vaccination.
The HAS recommends vaccination with the pre-pandemic Zoonotic Influenza Vaccine (H5N8) vaccine in the event of an increase in animal outbreaks, despite the barrier measures put in place, and in the presence of severe human cases in contact with these outbreaks (see scenario table 2.c) . This situation would in fact imply the need to protect exposed people , according to a two-dose vaccination schedule, spaced three weeks apart.
In this case, the HAS recommends prioritizing groups exposed to infection by the H5N1 virus:
The deployment of pre-pandemic vaccination among people exposed professionally must also be accompanied by active monitoring of the evolution of the circulating virus, monitoring of the safety of the vaccine and its acceptance and, finally, serological studies evaluating immune responses to determine the level and duration of the immune response in real conditions.
Regarding seasonal flu , the HAS reiterates that vaccination is still recommended for professionals exposed to swine and avian influenza viruses in order to reduce the risk of co-infection with human influenza viruses.
More broadly, the HAS emphasizes the importance of collaboration between national public and animal health organizations in order to combat this disease by adopting the "
One Health " approach which integrates human, animal and environmental health perspectives.
These recommendations are subject to revision depending on the evolution of the health situation. They are part of a pre-pandemic context and are not intended to define the vaccination strategy to adopt in the event of a possible pandemic. The health situation in other countries may have an impact on the vaccination strategy in France.
...
H5N1 Avian Flu: Vaccination Strategy for Possible Cases in People in Contact with Infected Animals
Press release - Posted on Apr 08 2025
April 8, 2025 H5N1 avian influenza continues to spread worldwide, particularly in the United States, where it affects several animal species and causes infections in people in close contact with infected animals. To date, no human-to-human transmission has been observed. In response to a request from the Ministry of Health, the French National Authority for Health (HAS) has developed, in anticipation, recommendations on the vaccination strategy that should be adopted in the event of possible human cases exposed to infected animals in France. The HAS defines several scenarios and recommends vaccinating people exposed to the virus with the pre-pandemic vaccine from Seqirus, in the event of an increase in animal outbreaks and in the presence of severe human cases in contact with these outbreaks.
The highly pathogenic avian influenza virus H5N1 is responsible for the widespread global circulation of avian influenza in birds. Since 2021, the virus has also affected a wide range of mammals (terrestrial, marine). Infections in humans are rare and occur mainly after direct contact with infected animals: this is referred to as zoonotic influenza . As of March 12, 2025, US authorities have recorded 70 human cases of clade 2.3.4.4b avian influenza, since the first case reported in April 2024. Other human cases have been identified worldwide, including one in Europe in early 2025, in the United Kingdom.
The objective of vaccination is primarily to prevent the development of severe forms in the event of contamination and, potentially, to reduce the risk of contamination of humans by animals. The Zoonotic Influenza Vaccine (H5N8) from Seqirus is the only pre-pandemic vaccine with marketing authorization in Europe. It is an inactivated vaccine with an adjuvant, which induces a cross-immune response against H5N1 strains circulating in the world. Although it remains impossible, at this stage, to accurately predict the evolution of the virus, the Ministry of Health has asked the HAS to develop recommendations in advance on the vaccination strategy in the event of the detection of a human case of zoonotic influenza in the territory, whether indigenous or imported . The HAS has thus defined several scenarios, the priority population groups and specified in which situation vaccination with the Seqirus vaccine is recommended. To this end, it has taken into consideration the latest epidemiological data, the availability of the vaccine and its data (immunogenicity, efficacy and tolerance), the opinion of experts interviewed as well as the vaccination recommendations issued internationally.
The HAS specifies that these recommendations do not address a pandemic situation resulting from the virus's ability to transmit from human to human.
Vaccination recommended in the event of a significant increase in animal outbreaks and severe human cases
The detection of a single human case of avian influenza in the territory, whether indigenous or imported, does not justify the implementation of pre-pandemic vaccination.
The HAS recommends vaccination with the pre-pandemic Zoonotic Influenza Vaccine (H5N8) vaccine in the event of an increase in animal outbreaks, despite the barrier measures put in place, and in the presence of severe human cases in contact with these outbreaks (see scenario table 2.c) . This situation would in fact imply the need to protect exposed people , according to a two-dose vaccination schedule, spaced three weeks apart.
In this case, the HAS recommends prioritizing groups exposed to infection by the H5N1 virus:
- Poultry (and cattle, where applicable) farmers
- Technical staff of veterinary diagnostic and research laboratories (autopsy, samples, experimentation)
- Laboratory personnel handling the virus as part of the investigation of human cases, including the National Reference Center (NRC)
- Poultry technicians and veterinarians
- Personnel carrying out emergency felling
- The knackers
The deployment of pre-pandemic vaccination among people exposed professionally must also be accompanied by active monitoring of the evolution of the circulating virus, monitoring of the safety of the vaccine and its acceptance and, finally, serological studies evaluating immune responses to determine the level and duration of the immune response in real conditions.
Regarding seasonal flu , the HAS reiterates that vaccination is still recommended for professionals exposed to swine and avian influenza viruses in order to reduce the risk of co-infection with human influenza viruses.
More broadly, the HAS emphasizes the importance of collaboration between national public and animal health organizations in order to combat this disease by adopting the "
One Health " approach which integrates human, animal and environmental health perspectives.
These recommendations are subject to revision depending on the evolution of the health situation. They are part of a pre-pandemic context and are not intended to define the vaccination strategy to adopt in the event of a possible pandemic. The health situation in other countries may have an impact on the vaccination strategy in France.
...