People with a significant history of allergies should not currently receive the Covid-19 vaccine from Pfizer Inc. and BioNTech SE, the U.K.’s National Health Service said, after two people experienced reactions from the shots. The warning came a day after the U.K. became the first western nation to begin a Covid vaccination program, following approval of the shot last week by the Medicines and Healthcare Products Regulatory Agency. Thousands of people received vaccinations on Tuesday, according to the NHS. “As is common with new vaccines, the MHRA have advised on a precautionary basis that people with a significant history of allergic reactions do not receive this vaccination,” Stephen Powis, national medical director for the NHS in England, said in a statement. June Raine, chief executive of the MHRA, said her team looked at two case reports of allergic reactions on Tuesday evening. Both of the people, staff members of the NHS, are recovering well. “We know from the very extensive clinical trials that this wasn’t a feature, that if we need to strengthen our advice now that we’ve had this experience in the vulnerable populations, we get that advice to the field immediately,” Raine told a panel of lawmakers. Pfizer and BioNTech said they’re supporting the MHRA in its investigation. The U.K. agency had already warned in its prescribing information that people who are allergic to any ingredients in the vaccine shouldn’t take it. Patients with a history of severe adverse reactions to a vaccine or severe allergic reactions to any component of the treatment were excluded from participating in the large study run by the companies before approval. “In the pivotal phase 3 clinical trial, this vaccine was generally well tolerated with no serious safety concerns reported by the independent data monitoring committee,” the companies said in a statement. Subscribe to our YouTube channel: https://bit.ly/2TwO8Gm Bloomberg Quicktake brings you live global news and original shows spanning business, technology, politics and culture. Make sense of the stories changing your business and your world. To watch complete coverage on Bloomberg Quicktake 24/7, visit http://www.bloomberg.com/qt/live, or watch on Apple TV, Roku, Samsung Smart TV, Fire TV and Android TV on the Bloomberg app. Have a story to tell? Fill out this survey for a chance to have it featured on Bloomberg Quicktake: https://cor.us/surveys/27AF30 Connect with us on… YouTube: https://www.youtube.com/user/Bloomberg Breaking News on YouTube: https://www.youtube.com/c/BloombergQuickTakeNews Twitter: https://twitter.com/quicktake Facebook: https://www.facebook.com/quicktake Instagram: https://www.instagram.com/quicktake