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9 October 2017
FAQ on the World Health Organization's recommendation on composition of 2018 southern hemisphere influenza vaccine  

  1. The composition of the seasonal influenza vaccine (SIV) recommended by the World Health Organization (WHO) for use in the 2018 southern hemisphere (SH) season is different from that for the 2017/18 northern hemisphere (NH) season purchased by the Government for use in Hong Kong. Can the SIV for the 2017/18 NH season to be used in Hong Kong offer protection against influenza in the coming winter season?
  2. Will the Government buy the 2018 southern hemisphere (SH) seasonal influenza vaccine (SIV) to strengthen influenza prevention?
  3. Can the public receive the southern hemisphere (SH) seasonal influenza vaccine (SIV), with the Singapore strain in it?
  4. Under the current situation, should the northern hemisphere (NH) seasonal influenza vaccine (SIV) or the southern hemisphere (SH) SIV be recommended?
  5. Hong Kong has purchased the northern hemisphere (NH) seasonal influenza vaccine (SIV) and will be used since October 2017. The vaccine component is different from the World Health Organization (WHO's recommendation for the southern hemisphere (SH) SIV. Is the SIV purchased by the Government a mismatch or is it purchased wrongly?

1. The composition of the seasonal influenza vaccine (SIV) recommended by the World Health Organization (WHO) for use in the 2018 southern hemisphere (SH) season is different from that for the 2017/18 northern hemisphere (NH) season purchased by the Government for use in Hong Kong. Can the SIV for the 2017/18 NH season to be used in Hong Kong offer protection against influenza in the coming winter season?

In September 2017, the WHO announced its recommendation for the 2018 SH SIV, in which the H3N2 component is the “Singapore” strain, while that for the NH SIV purchased by Hong Kong is the “Hong Kong” strain.  Both the Hong Kong strain and the Singapore strain are similar in their antigenic characteristics without antigen drift.  The Centre for Health Protection's virus characterisation has not detected significant antigenic changes in the circulating H3N2 viruses during the recent summer influenza season in Hong Kong.

Hong Kong has not yet entered the winter influenza season.  At present, here are not enough epidemiological and virological data and scientific evidence to predict the virus strain which will predominate.  It is too early to predict whether the strains of the NH SIV will match with the future circulating viruses. Nonetheless, SIV is safe and is one of the effective means to prevent seasonal influenza and its complications as well as to reduce influenza related hospitalisation and death.  When vaccine strains closely match with circulating viruses, the vaccine efficacy in individuals younger than 65 years of age typically ranges from 70-90%.  All members of the public aged 6 months or above, except those with known contraindications, are therefore recommended to receive SIV for personal protection.

 

2. Will the Government buy the 2018 southern hemisphere (SH) seasonal influenza vaccine (SIV) to strengthen influenza prevention?

The SIV for use in the 2018 SH season is not yet available. It is expected to be available in April 2018 and the winter influenza peak in Hong Kong may have already passed.  The predominating viruses in the coming winter in Hong Kong cannot be predicted.  Moreover, the Singapore strain and the Hong Kong strain are antigenically similar with no antigenic drift.  Any significant antigenic changes in H3N2 viruses circulating in the future may also render the SH SIV less effective against H3N2.

As such, there is not enough scientific ground to justify any purchase of the SH SIV at the present moment. The Centre for Health Protection (CHP) will continue to closely monitor the local and global influenza activities, predominating strains, vaccine effectiveness and relevant scientific literature. The CHP will consult the Scientific Committee on Vaccine Preventable Diseases and its Working Group on Influenza Vaccination if necessary.

 

3. Can the public receive the southern hemisphere (SH) seasonal influenza vaccine (SIV), with the Singapore strain in it?

The World Health Organization announced its recommendation for the SH SIV in September 2017. In general, it takes six to eight months for the production and regulatory approval of SIV. As such, there is still no supply of the 2018 SH SIV at the present moment.

 

4. Under the current situation, should the northern hemisphere (NH) seasonal influenza vaccine (SIV) or the southern hemisphere (SH) SIV be recommended?

As Hong Kong's geographical location is in the NH, it should follow the World Health Organization (WHO)'s recommendation in February 2017 and use the NH SIV to protect against influenza in the coming winter season.

The WHO recommends annual influenza vaccination. The main influenza season in Hong Kong in the past was the winter season, which occurred from January to March/April. People should receive SIV before winter season. The NH SIV is the only available SIV before the winter season in Hong Kong.

 

5. Hong Kong has purchased the northern hemisphere (NH) seasonal influenza vaccine (SIV) and will be used since October 2017. The vaccine component is different from the World Health Organization WHO)'s recommendation for the southern hemisphere (SH) SIV. Is the SIV purchased by the Government a mismatch or is it purchased wrongly?

The WHO reviews the global epidemiology of influenza twice a year, and recommends virus strains to be included in SIV for use in NH and SH respecitvely in accordance with the available data. The candidate seed strains will be sent to vaccine manufacturers for production. In general, it takes about 6 to 8 months for vaccine production and regulatory approval. In February 2017, the WHO made recommendations on the composition of the SIV for use in the 2017/18 NH influenza season. The NH SIV is the only vaccine available for use before the coming winter season in Hong Kong. Thus, the SIV purchased and to be used in Hong Kong (located in the northern hemisphere) for the 2017/18 influenza vaccination programme was based on the latest recommendations by the WHO. The vaccines have arrived in batches for use since October 2017, and the protection may also cover the next summer influenza season. On the other hand, the WHO's recent recommendation on the composition of the SH SIV is for vaccine manufacturer's reference to produce SIV for the 2018 SH influenza season. There is no SH SIV available for the time being.

 

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