How well does the vaccine protect you against Delta?

By Stuff reporter

The Whole Truth: Covid-19 Vaccination | By Stuff reporter Katie Kenny.


If you’re fully vaccinated against Covid-19, you might feel bulletproof even as the doubly-infectious Delta variant is circulating in the community. 

Fair enough - the Pfizer-BioNTech vaccine being rolled out across New Zealand is highly effective against the coronavirus.

But no vaccine works 100 per cent of the time. Scientists don’t yet know the relative role of vaccinated people in overall community transmission, but say it’s true that they can spread the virus.

One of the Covid-19 cases announced on Wednesday was a fully-vaccinated nurse at Auckland Hospital. This isn’t a failure of vaccination - the fact she wasn’t showing symptoms shows the vaccine did what it was meant to do: train her body to fight off and withstand an attack from the virus.

So, what do we know about how well the vaccine protects us against the Delta variant? 

Based on evidence from clinical trials in people 16 years and older, Pfizer’s vaccine was 95 per cent effective at preventing laboratory-confirmed infection with the SARS-CoV-2 virus (the virus that causes Covid-19), in people who received both doses and had no evidence of being previously infected. (That’s a 95 per cent reduction in risk compared to the baseline risk of an unvaccinated person.)

Real-world data then supported those findings, with the vaccine reducing the risk of Covid-19, including severe illness, by 90 per cent or more among people who were fully vaccinated. 

Scientists don’t have information from clinical trials about how well the leading Covid-19 vaccines perform against Delta, because the phase three trials were done before it became widespread. 

Observational data suggests the vaccines aren’t as good at preventing infections of the variant. Data out of Israel suggests a dramatic drop in the vaccine’s effectiveness. 

But there’s no evidence to suggest the vaccines are significantly less effective at preventing serious illness, hospitalisation and death. The Pfizer vaccine has been found to still prevent severe disease in more than nine out of 10 vaccinated people. 

This is the most important thing. And means vaccination will reduce the load on our health services.

Even one dose of the vaccine offers very high levels of protection against hospitalisation with the Delta variant. 

Fewer than 1 million New Zealanders have received both doses of the vaccine. Roughly 1.6 million have had their first jab. 

We know Māori and Pacific people face greater risk from Covid-19, but vaccination rates among these populations have been far from ideal.  

“Presently we just do not have enough of the population already double vaccinated to take any risks,” says Lesley Gray, a senior lecturer at Otago University’s Department of Primary Health Care and General Practice.