Comment from Professor Nikki Turner, Medical Director, Immunisation Advisory Centre

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Pfizer has recently released early information on its laboratory study of Omicron variant (1) of SARS-CoV-2 in November.

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Preliminary data from this unpublished laboratory study suggests that there may be reduced effectiveness from the current vaccination formulation to the Omicron variant - particularly against mild disease.

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This laboratory study has identified reduced responsiveness to neutralising antibody titre for the Omicron variant. High levels of neutralising antibodies are important to prevent entry of the virus into the body, so reduction in levels is likely to particularly affect mild and asymptomatic disease.

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Therefore these findings do suggest a likely reduction in vaccine effectiveness particularly for mild disease. However, immune response to disease also include cellular protection (T-cell immunity) and an important finding noted by the Pfizer/BioNTech company is that T-cell immunity appears to remain highly protective after a two dose course.

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This would suggest we can continue to expect reasonable protection to severe disease, which is a vital feature of an effective vaccine. This should continue to reassure us of the importance of continuing the heroic efforts of our vaccination programme to ensure as many of our population can access the vaccine as possible.

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A booster dose, or having previously had COVID, appears to be important in restoring much of the reduction in protection to the vaccine. There is a question as to when the best timing of a booster dose will be, many countries are considering what the best timing for a booster dose would be, and that is a decision that NZ is also currently reviewing.

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The important message is that we must continue to support as many New Zealanders as possible in receiving the primary course of vaccination followed by a booster dose. Further data will accumulate rapidly, allowing NZ to make a decision about the best timing of the booster dose that is expected to improve the protection for when we do see the Omicron strain in our community.

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