Question NW2398 to the Minister of Health
18 November 2021 - NW2398
Ismail, Ms H to ask the Minister of Health
What is the duration of vaccine immunity of the (a) Pfizer, (b) Moderna and (c) Johnson & Johnson vaccines?
Reply:
Conclusive evidence regarding the duration of immunity following immunisation against Covid-19 is not currently available.
Vaccine effectiveness has been shown to be maintained over time for severe/critical disease, but does diminish for mild-moderate disease. The durability of a particular vaccine is dependent on the variants of concern circulating at the time, and the durability of the immune response of the primary vaccine series.
It is also currently not known whether immunity induced by one vaccine will last longer than that induced by others. The vaccine effectiveness of the Moderna, Pfizer and Johnson & Johnson vaccines has remained relatively stable over time for protection against hospitalisation and death. There have been mild declines in effectiveness over time for hospitalisation and death for older people and those who are immunosuppressed. This has led to recommendations to provide booster doses to older people and those who are immunosuppressed and health care workers.
Such recommendations are country specific. Although vaccine effectiveness has remained durable over time for severe/critical disease, vaccine effectiveness against infection declined in the USA in the period when the Delta variant became dominant as compared to the pre-Delta period. This has led to the recommendation to provide booster doses as mentioned above.
It is difficult to extrapolate evidence of vaccine effectiveness from other regions to South Africa for the following reasons:
- their vaccine programmes started 4-6 months before the South African programme
- different variants have dominated in South Africa
- the high HIV prevalence in South Africa.
In South Africa, durability of effectiveness of the Johnson and Johnson vaccine against severe/critical disease during the Beta and Delta period was demonstrated in health care workers through the Sisonke study. The durability of the Pfizer vaccine during the Delta period has also been demonstrated. Ongoing monitoring is required to measure the duration of protection following immunisation with these vaccines.
END.