Are all viral vector vaccines a problem?

American health regulators have paused the use of the Johnson & Johnson coronavirus vaccine, following reports of rare blood clotting in six recipients. Like the AstraZeneca vaccine, Johnson & Johnson is what's known as a viral vector vaccine - where another virus is used like a taxi to deliver a bit of coronavirus to help teach the immune system. So on today's Coronacast, what are viral vector vaccines and could the rare blood-clots be a problem with them more broadly? Also on today's show: * What do the data show regarding the risks of clotting for people over the age of 50? * What can we learn from the US vaccine rollout? (We hear from special guest Anthony Fauci, who Tegan interviewed as part of an event presented by UNSW)