Johnson & Johnson, AstraZeneca PLC and the University of Oxford, along with outside scientists, are conducting early-stage research into whether potential modifications of their COVID-19 vaccines could reduce or eliminate the risk of rare but serious blood clots associated with the shots, according to people close to the process.
Fast-developing clues into how the clots form — driven in part by independent scientists in Europe, the U.S. and Canada — are boosting hopes of identifying the cause and possibly re-engineering AstraZeneca’s shot by next year, according to some of these people. It is too early to know whether either shot can be modified, or whether doing so would make commercial sense, these people say.