A vaccine is intended to provide immunity against COVID-19.  In general, vaccines contain weakened or inactive parts of a particular organism that triggers an immune response within the body. This weakened version will not cause the disease in the person receiving the vaccine, but it will prompt their immune system to respond. Some vaccines require multiple doses, given weeks or months apart. This is sometimes needed to allow for the production of long-lived antibodies and development of memory cells. In this way, the body is trained to fight the specific disease-causing organism, building up memory against the pathogen so it can fight it in the future.

The aim of vaccination is to prevent morbidity and mortality. It is also to achieve herd immunity and prevent ongoing transmission. When a person is vaccinated against a disease, their risk of infection is also reduced. Vaccinations help lower the possibility for a pathogen to circulate in the community and protect those who cannot be vaccinated due to health conditions such as allergies or their age.

There are a number of variants of COVID-19 that have arisen around the world.  No single vaccine will be effective against all the variants. South Africa’s vaccination campaign is guided by science and this means the country may need to change the choice of vaccine it uses. This was demonstrated in the case with the AstraZeneca vaccine, which was less effective against the 501Y.V2 variant while the Johnson & Johnson vaccine has proved effective against the COVID-19 501Y.V2 variant.

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