Uganda Health Minister Jane Ruth Aceng address the media after receiving a shipment of 1,200 doses for Ebola vaccine candidates, set to be used in a clinical trial, at the National Medical Stores (NMS) in Entebbe, Uganda, December 8, 2022. REUTERS/Abubaker Lubowa 

Uganda Health Minister Jane Ruth Aceng address the media after receiving a shipment of 1,200 doses for Ebola vaccine candidates set to be used in a clinical trial at the National Medical Stores (NMS) in Entebbe, Uganda, December 8, 2022. REUTERS/Abubaker Lubowa 

Uganda Health Minister Jane Ruth Aceng address the media after receiving a shipment of 1,200 doses for Ebola vaccine candidates, set to be used in a clinical trial, at the National Medical Stores (NMS) in Entebbe, Uganda, December 8, 2022. REUTERS/Abubaker Lubowa 

A consignment of 1,200 doses for Ebola vaccine candidates set to be used in a clinical trial is placed on a pallet at the National Medical Stores (NMS) in Entebbe, Uganda, December 8, 2022. REUTERS/Abubaker Lubowa 

Actor Amber Heard listens to her attorney's questions during the testimony of clinical and forensic psychologist Dr Shannon Curry (not pictured) during Depp's defamation trial against her, at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., May 25, 2022. REUTERS/Evelyn Hockstein/Pool 

Actor Amber Heard listens to her attorney's questions during the testimony of clinical and forensic psychologist Dr Shannon Curry (not pictured) during Depp's defamation trial against her, at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., May 25, 2022. REUTERS/Evelyn Hockstein/Pool 

Actor Johnny Depp reacts while clinical and forensic psychologist Dr Shannon Curry testifies during his defamation trial against his ex-wife Amber Heard, at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., May 25, 2022. REUTERS/Evelyn Hockstein/Pool 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Actor Johnny Depp's defamation trial against his ex-wife Amber Heard, at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., May 25, 2022. REUTERS/Evelyn Hockstein/Pool 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Actor Johnny Depp's defamation trial against his ex-wife Amber Heard, at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., May 25, 2022. REUTERS/Evelyn Hockstein/Pool 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Actor Johnny Depp's defamation trial against his ex-wife Amber Heard, at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., May 25, 2022. REUTERS/Evelyn Hockstein/Pool 

Clinical and forensic psychologist Dr. Shannon Curry looks on as she testifies during Johnny Depp's defamation trial against ex-wife Amber Heard at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., April 26, 2022. Brendan Smialowski/Pool via REUTERS 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Johnny Depp's defamation trial against ex-wife Amber Heard at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., April 26, 2022. Brendan Smialowski/Pool via REUTERS 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Johnny Depp's defamation trial against ex-wife Amber Heard at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., April 26, 2022. Brendan Smialowski/Pool via REUTERS 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Johnny Depp's defamation trial against ex-wife Amber Heard at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., April 26, 2022. Brendan Smialowski/Pool via REUTERS 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Johnny Depp's defamation trial against ex-wife Amber Heard at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., April 26, 2022. Brendan Smialowski/Pool via REUTERS 

Clinical and forensic psychologist Dr. Shannon Curry testifies during Johnny Depp's defamation trial against ex-wife Amber Heard at the Fairfax County Circuit Courthouse in Fairfax, Virginia, U.S., April 26, 2022. Brendan Smialowski/Pool via REUTERS 

A pack of Chinese traditional herbal medicine Jinhua Qinggan Granules (JHQG) for the treatment of coronavirus (COVID-19) disease, is displayed during a ceremony after completion of clinical trial on the efficacy and safety, at the International Centre for Chemical and Biological Sciences of Karachi University in Karachi, Pakistan, January 17, 2022. REUTERS/Akhtar Soomro 

Packs of Chinese traditional herbal medicine Jinhua Qinggan Granules (JHQG) for the treatment of coronavirus (COVID-19) disease are displayed during a ceremony after completion of clinical trial on the efficacy and safety, at the International Centre for Chemical and Biological Sciences of Karachi University in Karachi, Pakistan January 17, 2022. REUTERS/Akhtar Soomro 

Volunteer Mauricio Coppola, 38, Italian, receives a dose of the Soberana Plus vaccine during a clinical trial amid concerns about the spread of the coronavirus disease (COVID-19), in Havana, Cuba, November 16, 2021. REUTERS/Alexandre Meneghini 

Journalists wearing face masks amid the coronavirus disease (COVID-19) outbreak attend a conference, where the start of clinical trials for the Egyptian vaccine ''Coffee Fax'' is announced, at the National Research Center in Cairo, Egypt November 14, 2021. REUTERS/Shokry Hussien 

Egypt's Khaled Abdel Ghaffar, Minister of Higher Education and Scientific Research, who undertakes duties of Health Minister Hala Zayed, currently suffering from health problems, announces the start of clinical trials for the Egyptian vaccine ''Coffee Fax'' against the coronavirus disease (COVID-19) outbreak at the National Research Center in Cairo, Egypt November 14, 2021. REUTERS/Shokry Hussien 

Egypt's Khaled Abdel Ghaffar, Minister of Higher Education and Scientific Research, who undertakes duties of Health Minister Hala Zayed, currently suffering from health problems, announces the start of clinical trials for the Egyptian vaccine ''Coffee Fax'' against the coronavirus disease (COVID-19) outbreak at the National Research Center in Cairo, Egypt November 14, 2021. REUTERS/Shokry Hussien 

Egypt's Khaled Abdel Ghaffar, Minister of Higher Education and Scientific Research, who undertakes duties of Health Minister Hala Zayed, currently suffering from health problems, announces the start of clinical trials for the Egyptian vaccine ''Coffee Fax'' against the coronavirus disease (COVID-19) outbreak at the National Research Center in Cairo, Egypt November 14, 2021. REUTERS/Shokry Hussien 

A nurse prepares a dose of the Soberana 02 vaccine during its clinical trials at a hospital amid concerns about the spread of the coronavirus disease (COVID-19) in Havana, Cuba, June 29, 2021. REUTERS/Alexandre Meneghini 

People sit next to a sign announcing the clinical trials of the Soberana 02 vaccine at a hospital amid concerns about the spread of the coronavirus disease (COVID-19) in Havana, Cuba, June 29, 2021. REUTERS/Alexandre Meneghini 

Cristian Artimbau, 14, gets a dose of the Soberana 02 vaccine during its clinical trials at a hospital amid concerns about the spread of the coronavirus disease (COVID-19) in Havana, Cuba, June 29, 2021. REUTERS/Alexandre Meneghini 

People are seen in a clinic where the Soberana-02 COVID-19 vaccine is being tested, as part of Phase III trials of the experimental Cuban vaccine candidate, amid concerns about the spread of the coronavirus disease, in Havana, Cuba, March 24, 2021. Ramon Espinosa / Pool via REUTERS 

A health worker is seen at the clinic where people are receiving the Soberana-02 COVID-19 vaccine, as part of Phase III trials of the experimental Cuban vaccine candidate, amid concerns about the spread of the coronavirus disease, in Havana, Cuba, March 24, 2021. Ramon Espinosa / Pool via REUTERS 

People are seen in a clinic where the Soberana-02 COVID-19 vaccine is being tested as part of Phase III trials of the experimental Cuban vaccine candidate, amid concerns about the spread of the coronavirus disease, in Havana, Cuba, March 24, 2021. Ramon Espinosa / Pool via REUTERS 

View of items for Johnson & Johnson's COVID-19 vaccine clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters' senior correspondent Aislinn Laing leaves a medical facility after receiving a dose of vaccine or placebo for a Johnson & Johnson's COVID-19 vaccine clinical trial in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

View of items for Johnson & Johnson's COVID-19 vaccine clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters' senior correspondent Aislinn Laing waits after receiving a dose of vaccine or placebo for a Johnson & Johnson's COVID-19 vaccine clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Blood samples from volunteers who will receive a dose of vaccine or placebo for Johnson & Johnson's clinical trial of a coronavirus disease (COVID-19) vaccine are pictured inside a medical facility at Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

A nurse takes a nasal sample from Reuters senior correspondent Aislinn Laing before she receives a vaccine or placebo dose for Johnson & Johnson's COVID-19 vaccine clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

A "vaccination" hangs inside a medical facility to enrol participants and administer a dose of a vaccine or placebo for Johnson & Johnson's COVID-19 vaccine clinical trial at Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

A nurse sets up for Johnson & Johnson's COVID-19 vaccine clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters senior correspondent Aislinn Laing prepares to give a blood sample at a medical facility before receiving a dose of vaccine or placebo of Johnson & Johnson's COVID-19 vaccine clinical trial at Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters senior correspondent Aislinn Laing waits after receiving a dose of a COVID-19 vaccine or placebo for Johnson & Johnson's clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters senior correspondent Aislinn Laing receives a dose of vaccine or placebo for a Johnson & Johnson's COVID-19 vaccine clinical trial at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters senior correspondent Aislinn Laing gives a blood sample at a medical facility before receiving a dose of vaccine or placebo of Johnson & Johnson's COVID-19 vaccine clinical trial at Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

A nurse holds a syringe used to shoot a dose of vaccine, or placebo of Johnson & Johnson's clinical trial for a coronavirus disease (COVID-19) vaccine to Reuters senior correspondent Aislinn Laing at a medical facility in Colina area, Santiago, Chile, November 20, 2020. Picture taken November 20, 2020. REUTERS/Ivan Alvarado 

Reuters journalist Steve Stecklow participates in a clinical trial of the experimental Novavax COVID-19 vaccine at the NIHR/Wellcome King's Clinical Research Facility in London, Britain, October 28, 2020. Picture taken October 28, 2020. REUTERS/Steve Stecklow 

Reuters journalist Steve Stecklow participates in a clinical trial of the experimental Novavax COVID-19 vaccine at the NIHR/Wellcome King's Clinical Research Facility in London, Britain, October 28, 2020. Picture taken October 28, 2020. REUTERS/Steve Stecklow 

A nurse shows a box with Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) prepared for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse holds a box with Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) prepared for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. A sign on a fridge reads " The vaccine is stored here". REUTERS/Tatyana Makeyeva 

A nurse inoculates a volunteer with Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse shows a box with Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) prepared for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse shows Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) prepared for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse prepares Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse prepares Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse shows Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) prepared for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse shows Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) prepared for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

A nurse prepares Russia's "Sputnik-V" vaccine against the coronavirus disease (COVID-19) for inoculation in a post-registration trials stage at a clinic in Moscow, Russia September 17, 2020. REUTERS/Tatyana Makeyeva 

Robyn Porteous, a vaccine trials' volunteer, is injected with a vaccine as part of the country's human clinical trial for potential vaccines after being tested for the coronavirus disease (COVID-19), at the Wits RHI Shandukani Research Centre in Johannesburg, South Africa, August 27, 2020. Picture taken August 27, 2020. REUTERS/Siphiwe Sibeko TPX IMAGES OF THE DAY 

A health worker holds a COVID-19 sample collection kit of a vaccine trials' volunteer, after they were tested for the coronavirus disease and take part in the country's human clinical trial for potential vaccines at the Wits RHI Shandukani Research Centre in Johannesburg, South Africa, August 27, 2020. Picture taken August 27, 2020. REUTERS/Siphiwe Sibeko 

A health worker talks to a vaccine trials' volunteer before he is tested for the coronavirus disease (COVID-19) and takes part of the country's human clinical trial for potential vaccines at the Wits RHI Shandukani Research Centre in Johannesburg, South Africa, August 27, 2020. Picture taken August 27, 2020. REUTERS/Siphiwe Sibeko 

Robyn Porteous, a vaccine trials' volunteer, is tested for the coronavirus disease (COVID-19) before being injected with a vaccine as part of the country's human clinical trial for potential vaccines at the Wits RHI Shandukani Research Centre in Johannesburg, South Africa, August 27, 2020. Picture taken August 27, 2020. REUTERS/Siphiwe Sibeko 

A syringe with a vaccine is seen ahead of trials by volunteers testing for the coronavirus disease (COVID-19), and taking part in the country's human clinical trial for potential vaccines at the Wits RHI Shandukani Research Centre in Johannesburg, South Africa, August 27, 2020. Picture taken August 27, 2020. REUTERS/Siphiwe Sibeko 

A doctor takes part in a demonstration for Reuters of ongoing clinical trials led by Sheba Medical Center and Israeli firm Newsight Imaging, in which they say a newly developed saliva test aims to determine in less than a second whether or not you are infected with the coronavirus disease (COVID-19), at Tel Hashomer in Ramat Gan, Israel August 13, 2020. REUTERS/Ammar Awad