The most important goal of vaccination is to stop people getting seriously sick and dying. And we know the Pfizer Covid-19 vaccine is incredibly effective at that, preventing hospitalisation more than 90 per cent of the time.
But preventing people catching the virus is also important, as that’s how you stop outbreaks from spreading.
Before vaccines, the only way to do that was with lockdowns.
Vaccination can help reduce transmission in two ways. The first is by stopping people getting infected with SARS-CoV-2, the virus that causes Covid-19. Obviously if you don’t get the virus in the first place, you can’t give it to someone else.
The numbers are hard to pin down. Research suggests the Pfizer vaccine can prevent about 70 per cent of infections, but that wanes over time.
There’s a second potential benefit to vaccination. Even if you’re unlucky enough to get Covid-19 after being fully vaccinated, the hope is that you’ll get milder disease and be less likely to pass it on.
There’s good and bad news on that front.
A British study of household contacts found vaccinated people who got breakthrough Covid infections did not get seriously ill. However, they were just as likely as unvaccinated, infected people to pass the virus on to their housemates.
Experts think that’s because the Delta variant replicates at breakneck speed.
Vaccination for Covid-19 creates an immune memory, which teaches the body’s disease-fighting cells to make antibodies when the virus is detected in future. But that process takes time.
So with Delta, infection can set in before the immune response has time to ramp up.
Several studies have shown that fully vaccinated people who catch Delta, have about the same peak amount of virus in their systems as unvaccinated people who get infected.
But the good news is that vaccinated people shake off the virus more quickly. That means you're infectious for a shorter period, so there's less time to pass it on.
So being vaccinated doesn’t make it impossible for you to get Covid-19, or give it to others. But it does reduce the risk significantly. You still need to wear a mask and socially distance, to prevent the virus spreading.
Vaccination is still the best thing you can do to reduce your chances of giving the virus to someone you care about.
Reporting disclosure statement: This post was reviewed by The Whole Truth: Covid-19 Vaccination expert panel member Dr Dianne Sika-Paotonu, an immunologist and senior lecturer in pathology and molecular medicine at Otago University.