Covid booster shots: why, when and how much?

The Covid vaccine roll out continues at pace, but at what point should we start planning for covid booster shots? An Oxford University study published last month found Covid vaccines do not protect people as well even after three months. It found the Pfizer vaccine was 75 percent effective in preventing infection after 90 days, down from 85 percent two weeks after the second shot. The study is not yet peer-reviewed. In the United Kingdom, half a million people with weakened immunity are being offered a third dose of the vaccine in order to improve their protection against the virus, and health officials are discussing whether to roll out a booster programme. Our Covid 19 Response Minister Chris Hipkins has said New Zealand could have as many as two million doses left over for use as boosters if the science and officials recommend it. Meanwhile the WHO is asking wealthy countries to delay buying excess supplies to ensure poorer countries can at least get their first and second shots. Kathryn speaks with Professor David Hunter is a Professor of Epidemiology at Oxford University and Professor of Medicine, Emeritus at Harvard Medical School.