Main takeaways about Covid vaccines so far There are important, often major, differences in the characteristics and effects of the vaccines.2 vaccines have been convincingly shown to have high efficacy against getting sick with Covid-19 – BNT/Pfizer’s and NIH/Moderna’s.There is a material difference in the rate of adverse events reported between those 2 vaccines:Most people had adverse events after the BNT/Pfizer vaccine, but they were generally not severe;NIH/Moderna adverse events were more frequent and severe – severe adverse events were common.There are too many question marks around the trials of another 2 vaccines to be confident about results – Oxford/AstraZeneca’s and Sputnik V.2 inactivated virus vaccines from China are reported to have good efficacy and very low adverse events, but the data to substantiate that isn’t public. Other types of vaccines anticipated to also have lower rates of adverse events don’t have phase 3 results yet either, but could be public in the next few weeks.We don’t know to what extent being vaccinated with any of these vaccines reduces the risk of a person spreading Covid-19 if they don’t know they’re infected – but the vast majority of virus transmission is from people with symptoms.We don’t know much about the effects of these vaccines in young children, for people on immunosuppressant medication (including steroids and cancer medications), and in pregnancy and breastfeeding. (A trial of Moderna’s vaccine in people with cancer is being discussed.) We don’t know how long immunity will last.