How do vaccine responses vary?
Scientists don’t yet understand exactly how the body builds immunity to Covid-19. ‘‘We think it’s neutralising antibodies, but we’re not sure,’’ says Dr Fran Priddy, clinical director of Vaccine Alliance Aotearoa New Zealand at the Malaghan Institute.
It’s not unusual for vaccine immune responses to vary, with some people producing as little as half as many antibodies, Priddy says.
The science isn’t yet advanced enough to predict whose immune systems will mount a gutsy response. But antibody production can decline with age, and obese people can also have a lower immune response.
Priddy is running a study in Rotorua and Christchurch investigating New Zealanders’ Covid vaccine responses.
A one-month post-vaccine snapshot should indicate whether our antibody production is similar to populations overseas. Follow-up of 6-12 months will show how that immune response might wane.
The study is focused on Ma¯ori, Pasifika and older people, as they’re more likely to get very sick or die if they contract Covid19.
The tricky thing is that no-one knows what antibody level is
protective against Covid-19. So even a 50 per cent reduction in antibody levels might not make a vaccine ineffective, Priddy says. ‘‘That doesn’t mean they’re not protected, even though that sounds huge.’’
What it might mean, though, is that protection wears off more quickly. If someone has an initial response of 500, and that falls off by 100 points a month, their immunity will wane more quickly than someone with a starting response of 1000.
But it’s still worth getting vaccinated, as it will help prevent severe disease and limit the development of new variants, she says. ‘‘The answer to every question is ‘Get the vaccine’.’’