<span style="color: #222222;">Britain launched a trial today to assess the immune responses generated if doses of the COVID-19 vaccines from Pfizer Inc and AstraZeneca Plc are combined in a two-shot schedule. The British researchers behind the trial said data on vaccinating people with the two different types of coronavirus vaccines could help understanding whether shots can be rolled out with greater flexibility around the world. Initial data on immune responses is expected to be generated around June. </span><br />'' <br />'' <span style="color: #222222;">The trial will examine the immune responses of an initial dose of Pfizer vaccine followed by a booster of AstraZeneca's, as well as vice versa, with intervals of 4 and 12 weeks.</span><br />'' <span style="color: #222222;"> </span><br />'' <span style="color: #222222;">Both the mRNA shot developed by Pfizer and Biontech and the adenovirus viral vector vaccine developed by Oxford University and AstraZeneca are currently being rolled out in Britain, with a 12-week gap between two doses of the same vaccine. It is expected more vaccines will be added to the trial when they are approved and rolled out. The trial will not assess the overall efficacy of the shot combinations, but researchers will measure antibody and T-cell responses, as well as monitor for any unexpected side effects. </span><br />'' <br />'' <span style="color: #222222;">The trial is looking to recruit people over the age of 50 who may be at higher risk than younger people and have not been vaccinated already. AstraZeneca's shot is also being tested in combination with Russia's Sputnik V vaccine, and British drugmaker's research chief has said more studies on combining vaccines should be done.</span><br />''