- planned receipt of any vaccine other than the study intervention within 30 days before and after each study vaccination with the exception of the licensed seasonal influenza vaccination and the licensed pneumococcal vaccine. participants will be encouraged to receive this vaccination at least 7 days before or after their study vaccine. - prior or concomitant vaccine therapy for covid-19 - icu patients - hemodynamically unstable patients, shock - significant encephalopathy, acute kidney injury - documented or suspected sepsis including chest infection - aclf (acute on chronic liver failure) - significant cardiac or respiratory co-morbidities - known allergy to vaccination - prior receipt of an investigational or licensed vaccine likely to impact on interpretation of the trial data (e.g. adenovirus vectored vaccines, any coronavirus vaccines). - history of allergic disease or reactions likely to be exacerbated by any component of the azd1222 (covishield) vaccine. - any history of angioedema. - any history of anaphylaxis. - pregnancy, lactation or willingness/intention to become pregnant during the study. - any other serious chronic illness requiring hospital specialist supervision. - currently or in last 3 weeks have: fever/cough/sorethroat/rhinorrhea/hemoptysis/breathlessness/chest pain/myalgia/nausea/vomiting/diarrhea/abdominal pain/loss of taste

- planned receipt of any vaccine other than the study intervention within 30 days before and after each study vaccination with the exception of the licensed seasonal influenza vaccination and the licensed pneumococcal vaccine. participants will be encouraged to receive this vaccination at least 7 days before or after their study vaccine. - prior or concomitant vaccine therapy for covid-19 - icu patients - hemodynamically unstable patients, shock - significant encephalopathy, acute kidney injury - documented or suspected sepsis including chest infection - aclf (acute on chronic liver failure) - significant cardiac or respiratory co-morbidities - known allergy to vaccination - prior receipt of an investigational or licensed vaccine likely to impact on interpretation of the trial data (e.g. adenovirus vectored vaccines, any coronavirus vaccines). - history of allergic disease or reactions likely to be exacerbated by any component of the azd1222 (covishield) vaccine. - any history of angioedema. - any history of anaphylaxis. - pregnancy, lactation or willingness/intention to become pregnant during the study. - any other serious chronic illness requiring hospital specialist supervision. - currently or in last 3 weeks have: fever/cough/sorethroat/rhinorrhea/hemoptysis/breathlessness/chest pain/myalgia/nausea/vomiting/diarrhea/abdominal pain/loss of taste