EXPLAINER: Why countries are halting the AstraZeneca shot
FILE - In this Feb. 5, 2021, file photo, vials AstraZeneca vaccine ready to be used at the Wellcome Centre in London. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots. Britain and several other countries have stuck with the vaccine. (AP Photo/Frank Augstein, File)

FILE - In this Feb. 5, 2021, file photo, vials AstraZeneca vaccine ready to be used at the Wellcome Centre in London. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots. Britain and several other countries have stuck with the vaccine. (AP Photo/Frank Augstein, File)

Mar. 15, 2021 08:23 AM EDT
FILE - In this Jan. 11, 2021, file photo, a man receives an injection of the AstraZeneca vaccine at the mass vaccination program in Newcastle Upon Tyne, England. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots.​ Britain and several other countries have stuck with the vaccine. (AP Photo/Scott Heppell, File)

FILE - In this Jan. 11, 2021, file photo, a man receives an injection of the AstraZeneca vaccine at the mass vaccination program in Newcastle Upon Tyne, England. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots.​ Britain and several other countries have stuck with the vaccine. (AP Photo/Scott Heppell, File)

Mar. 15, 2021 08:33 AM EDT
Health workers administer doses of the AstraZeneca vaccine against COVID-19 inside the convention center known as "La Nuvola", The Cloud, in Rome, Wednesday, March 10, 2021. The visually extraordinary complex designed by famed architect Massimiliano Fuksas has been transformed into a temporary vaccination center. (AP Photo/Andrew Medichini)

Health workers administer doses of the AstraZeneca vaccine against COVID-19 inside the convention center known as "La Nuvola", The Cloud, in Rome, Wednesday, March 10, 2021. The visually extraordinary complex designed by famed architect Massimiliano Fuksas has been transformed into a temporary vaccination center. (AP Photo/Andrew Medichini)

Mar. 10, 2021 08:49 AM EST
A medical staff dispays AstraZeneca COVID-19 vaccine at a vaccination site set up in the Marseille soccer Velodrome stadium, during a presentation to the media, in Marseille, Monday, March 15, 2021. The government plans to inoculate 10 million citizens by mid-April, 20 million by mid-May and a total of 30 million, or two-thirds of the adults by summer. (AP Photo/Daniel Cole)

A medical staff dispays AstraZeneca COVID-19 vaccine at a vaccination site set up in the Marseille soccer Velodrome stadium, during a presentation to the media, in Marseille, Monday, March 15, 2021. The government plans to inoculate 10 million citizens by mid-April, 20 million by mid-May and a total of 30 million, or two-thirds of the adults by summer. (AP Photo/Daniel Cole)

Mar. 15, 2021 07:58 AM EDT
FILE - In this Jan. 2, 2021, file photo, doses of the COVID-19 vaccine developed by Oxford University and U.K.-based drugmaker AstraZeneca arrive at the Princess Royal Hospital in Haywards Heath, England. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots. Britain and several other countries have stuck with the vaccine. ​(Gareth Fuller/Pool Photo via AP, File)

FILE - In this Jan. 2, 2021, file photo, doses of the COVID-19 vaccine developed by Oxford University and U.K.-based drugmaker AstraZeneca arrive at the Princess Royal Hospital in Haywards Heath, England. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots. Britain and several other countries have stuck with the vaccine. ​(Gareth Fuller/Pool Photo via AP, File)

Mar. 15, 2021 08:32 AM EDT
A health worker administers a dose of the AstraZeneca vaccine against COVID-19 to a patient at a drive-through vaccination center, in Milan, Italy, Monday, March 15, 2021. Half of Italy's regions have gone into the strictest form of lockdown in a bid to curb the latest spike in coronavirus infections that have brought COVID-19 hospital admissions beyond manageable thresholds. (Claudio Furlan/LaPresse via AP)

A health worker administers a dose of the AstraZeneca vaccine against COVID-19 to a patient at a drive-through vaccination center, in Milan, Italy, Monday, March 15, 2021. Half of Italy's regions have gone into the strictest form of lockdown in a bid to curb the latest spike in coronavirus infections that have brought COVID-19 hospital admissions beyond manageable thresholds. (Claudio Furlan/LaPresse via AP)

Mar. 15, 2021 08:42 AM EDT
FILE - In this March 2, 2021, file photo, a police officer receives an injection with AstraZeneca's COVID-19 vaccine in Munich, Germany. After saying last week they would continue with the vaccine, German officials said Monday, March 15, they would suspend its use after new reports of problems, based on the advice from its medicines regulator. (Sven Hoppe/dpa via AP, File)

FILE - In this March 2, 2021, file photo, a police officer receives an injection with AstraZeneca's COVID-19 vaccine in Munich, Germany. After saying last week they would continue with the vaccine, German officials said Monday, March 15, they would suspend its use after new reports of problems, based on the advice from its medicines regulator. (Sven Hoppe/dpa via AP, File)

Mar. 15, 2021 11:39 AM EDT
FILE - In this March 12, 2021, file photo, a health worker holds a bottle of AstraZeneca COVID-19 vaccine with name Thailand's Prime Minister Prayuth Chan-ocha written on it, at Bamrasnaradura Hospital in Bangkok, Thailand. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots. (AP Photo/Sakchai Lalit, File)

FILE - In this March 12, 2021, file photo, a health worker holds a bottle of AstraZeneca COVID-19 vaccine with name Thailand's Prime Minister Prayuth Chan-ocha written on it, at Bamrasnaradura Hospital in Bangkok, Thailand. In recent days, countries including Denmark, Ireland and Thailand have temporarily suspended their use of AstraZeneca's coronavirus vaccine after reports that some people who got a dose developed blood clots, even though there's no evidence that the shot was responsible. The European Medicines Agency and the World Health Organization say the data available do not suggest the vaccine caused the clots. (AP Photo/Sakchai Lalit, File)

Mar. 15, 2021 08:23 AM EDT