Researchers in Japan have warned that Tokyo's Olympic and Paralympic Games, which is set to start in July 2021, may need canceling if the rollout of vaccination to protect against coronavirus disease 2019 (COVID-19) continues at the slow pace it is now.
"Vaccine rollout has been slow in Japan, compared to other developed countries," says Yasuharu Tokuda from Muribushi Okinawa Center for Teaching Hospitals and Toshikazu Kuniya from Kobe University.
The team's predictive analysis of the epidemic in Tokyo forecast that if vaccination rollout continues at the current pace, then the maximum daily number of new infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent that causes COVID-19 – would reach almost 8,000 in the city during August of 2021.
The researchers say that this daily number is more than the highest number recorded (2,447) on the 7th of January when the Tokyo healthcare system was overwhelmed.
However, if the rollout pace could be doubled, the maximum daily number of new cases would be around 4,500 in August, and if it were quadrupled, the maximum daily number would be around 2,000.
The team warns that the pace of vaccination should quickly be increased to prevent local healthcare systems from becoming overwhelmed.
If vaccine rollout cannot be enhanced, then cancellation may be the only acceptable option, add the researchers.
A pre-print version of the research paper is available on the medRxiv* server, while the article undergoes peer review.
Infections recently increased in Japan
Tokyo's Olympic and Paralympic Games is set to launch in late July this year (2021), without spectators from abroad attending.
However, the incidence of SARS-CoV-2 cases in Japan has increased in recent weeks as the country experiences a "fourth wave" of the COVID-19 epidemic.
Furthermore, vaccine rollout has been slow in Japan, compared with other developed countries.
"Japan does not produce domestic anti-COVID-19 vaccines and we import and provide mRNA vaccines to people (first healthcare workers, followed by the elderly). That started on February 17th, 2021," write the researchers.
The team says the situation is concerning since there could be a significant surge in infections in Tokyo during the Games. Local healthcare systems would then be overwhelmed, and fewer healthcare workers would be available during the Games. Moreover, athletes, coaches, judges, and journalists would face a greater risk of infection.
The number of newly reported or predicted daily cases of COVID-19 in Tokyo
What did the study involve?
The team developed a COVID-19 epidemic curve (a statistical chart of outbreak progression over time) in Tokyo based on weekly data reported from the 23rd of January 2020 up to the 16th of April, 2021.
A "susceptible-exposed-infected-removed" compartmental model was used for the curve fitting by updating the estimation every week.
The rates of transition from "exposure" to "infection" and from "infection" to "removed" were set such that the average period of incubation and infection was five days and ten days, respectively.
The epidemic curve after April 17th was predicted by calculating the average of the infection rates over the previous three weeks.
What did they find?
The curve predicted that if vaccine rollout continues at the current pace – 1 in 1,000 adults per day – the maximum daily number of new SARS-CoV-2 infections in August would be 7,991.
"This daily number is greater than the highest daily cases (2,447) recorded on January 7th," says the team. "During that month in Tokyo, the healthcare system was overwhelmed."
However, if the rollout pace could be doubled (1/500 per day), the maximum number of daily new cases would be 4,470 in August.
If it could be quadrupled (1/250 per day), the maximum daily number would be 2,128 in July and 1,977 in August.
In these accelerated pace scenarios, subsequent cases would be decreasing thereafter, adds the team.
The Games may need canceling if vaccination cannot be expedited
"Based on our predictive analysis, the vaccination speed in Tokyo should be rapidly increased to mitigate a COVID-19 surge and to prevent an overwhelmed local healthcare system and less availability of healthcare workers during the time of the Games," said the researchers.
This might lower the risk of infection among athletes and all people involved in the Games, they add.
"If vaccine rollout cannot be enhanced before the Games, cancellation might be an acceptable decision. After all, health is most precious to our Olympians," concludes the team.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.