Coronavirus updates: 1st vaccines now on the way to all 50 US states

An 83-year-old passenger on board Royal Caribbean International’s Quantum of the Seas tested positive for COVID-19 on Wednesday, Singapore's Ministry of Health said in a statement.

The passenger had reported to the ship medical center with symptoms and was tested with PCR equipment on board. The 83-year-old was immediately isolated after getting the results.

Close contacts of the individual have tested negative and have been quarantined.

Singapore's National Public Health Laboratory will re-test that sample and a second sample will be taken to verify the results.

An epidemiological investigation has been initiated and contact tracing is in progress, the Ministry of Health said. All passengers will undergo mandatory COVID-19 testing before they are allowed to leave the terminal at Marina Bay Cruise Centre.

The ship will go through a "deep cleaning and disinfection," the cruise line said in a statement.

"The health and safety of our guests and crew are of utmost importance to us, and we have made the decision to cancel the 4-night cruise departing tomorrow, December 10," Royal Caribbean said.

ABC News' Christine Theodorou contributed to this report.

Authorities in the U.K. were investigating reports of two allergic reactions to the coronavirus vaccine from Pfizer/BioNTech -- a day after the country started its historic inoculation program.

Dr. June Raine, head of the UK regulatory body Medicines and Healthcare products Regulatory Agency (MHRA), said the agency was looking at two reports of allergic reactions to the vaccine, which rolled out yesterday.

"We know from the very extensive clinical trials that this wasn’t a feature but if we need to strengthen our advice... we get that advice to the field immediately,” said Raine.

The vaccine is believed to be both safe and 95% effective, according to Pfizer/BioNTech. The U.S. Food and Drug Administration was set to hold a hearing for emergency use of the drug on Thursday.

“There have been two cases of anaphylactoid reactions in individuals with a strong past history of allergic reactions both of whom carried an adrenaline auto injector,” the National Health Service (NHS) said in a statement on Wednesday. “These individuals developed symptoms of anaphylactoid reaction shortly after receiving the vaccine. Both recovered after appropriate treatment. We are seeking further information and will issue further advice following investigation.”

Pfizer/BioNTech have not yet commented on these latest findings.

Professor Stephen Powis, national Medical Director for the NHS, said: “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 after two people with a history of significant allergic reactions responded adversely yesterday. Both are recovering well.”

Russia registered 26,190 new coronavirus infections and 559 fatalities linked with the virus over the past 24 hours, officials said on Wednesday. 

In Moscow, 5,145 new infections and 75 fatalities have been confirmed over the same time, according to official information. 

The all-time high of 29,000 new cases was registered just last weekend but since then the number has been declining. 

Since the start of the pandemic, Russia has confirmed 2,541,199 coronavirus infections and 44,718 deaths, officials have said.

ABC News' Alina Lobzina contributed to this report.

Former U.N. Ambassador Nikki Haley has announced on Twitter that her sister-in-law Rhonda Lee Nelson has died from COVID-19.

Nelson, 53, who passed away on Nov. 25, resided in West Milton, Ohio, according to the Associated Press, and was a singer and piano musician who "ministered to many inside and outside of the church."

“Today we said goodbye to Michael’s sister, Rhonda, who passed the day before Thanksgiving of Covid. She ministered to many inside and outside of the church. She loved God, her family & all who knew her. She will be missed,” Haley said in her tweet.

No other details were provided regarding Nelson’s death but the seven-day rolling average of daily new cases in the state of Ohio has been on the rise in recent weeks, according to the Associated Press, and one in every 193 people in the state have tested positive for the novel coronavirus in just the past week alone.