Statistics about the Oxford/AstraZeneca vaccine have dominated the news, with concern over blood clots leading many European countries to suspend its use. Then, on Thursday, the European Medicines Agency (EMA) and the UK Medicines and Healthcare products Regulatory Agency (MRHA) declared there was no general increased risk of thromboses, but they were continuing to look at a rare type of clotting linked with low platelets, particularly in the brain. From nearly 12m Oxford/AZ vaccinations up to 7 March, the UK “yellow card” system has recorded 61,000 reports detailing 228,000 reactions, around double the rate for the Pfizer/BioNTech vaccine. There have been huge numbers of immediate side-effects such as pain, nausea, fatigue, headache and fever, with other notable reports including palpitations (1,318), “feeling jittery” (10), “screaming” (4), chilblains (10), alcohol poisoning (2), libido increased (1), libido decreased (1), and one remarkable report of a pregnancy following vaccination. But some have been serious events, including 289 deaths soon after the jab, and all of these will have been examined carefully. Every decision has trade-offs. Both UK vaccines have had more than 200 severe allergic reactions (anaphylaxis), which is why we have to sit for 15 minutes after the jab. So it’s reasonable that, rather than saying the vaccine is “safe”, the EMA and MRHA emphasise that the benefits of the vaccine outweigh the risks of side-effects. In the UK there has been one of these rare blood reactions in 2m jabs. But for every 2 million people in their 50s getting a jab, the current group being vaccinated, we would currently expect to prevent around five deaths a week. The ratio of benefit to harms is high, and even higher on mainland Europe as their third wave starts. The “cautionary” pause in many countries may mean increased vaccination hesitancy. France has moved from initially not approving the Oxford/AZ vaccine for over-65s, to pausing it for everyone, to now not approving it for under-55s. It would not be surprising if people are confused by this. Confidence can shatter like glass and be hard to remake. David Spiegelhalter is chair of the Winton Centre for Risk and Evidence Communication at Cambridge. Anthony Masters is statistical ambassador for the Royal Statistical Society