They recommended that the United States prepare for the worst-case scenario that would include a second great wave of coronavirus infections in the fall and winter. Even at the best of times, people will continue to die from the virus, they predicted.
“This thing will not stop until it infects 60-70% of people,” Mike Osterholm, director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota, told CNN.
Osterholm has been writing about the risk of a pandemic for 20 years and has advised several presidents. He wrote the report with Harvard School of Public Health epidemiologist Marc Lipsitch, who is also a leading pandemic expert; Dr. Kristine Moore, former epidemiologist with the Centers for Disease Control and Prevention, who is now CIDRAP’s medical director; and historian John Barry, who wrote the 2004 book “The Big Flu” on the 1918 flu pandemic.
Waiting for collective immunity
Because Covid-19 is new, no one has immunity, they said. “The duration of the pandemic is likely to be 18 to 24 months, as collective immunity gradually develops in the human population,” they wrote.
Their predictions are different from the models presented by groups such as the Institute for Health Metrics and Evaluation (IHME) at the University of Washington or the models produced by Imperial College London, including the report predicting millions of deaths in the States United States and the United Kingdom helped galvanize responses in the two governments.
The CIDRAP-led team used these reports, historical data from past pandemics, and published reports on the medical details of Covid-19 to make their predictions.
“I have been saying for a long time that when you are trying to understand how infectious diseases will develop, you have to trust the story as well as the models,” Lipsitch told CNN. For example, pandemic infections do not tend to die in the summer, as does seasonal flu.
Covid-19 is more like a pandemic flu strain, they said.
“Due to a longer incubation period, more asymptomatic spread and higher R0, COVID-19 appears to be spread more easily than the flu,” they wrote in the report. R0 is the average number of other people infected by each patient.
“A higher R0 means that more people will need to be infected and immunized before the pandemic can end,” they add. “Based on the most recent flu pandemics, this epidemic is likely to last 18 to 24 months.”
Prepare for the worst
They said government officials should stop telling people that the pandemic could end and prepare citizens for the long term.
Three scenarios are possible, they said:
Scenario 1: The first wave of Covid-19 in the spring of 2020 is followed by a series of small repetitive waves that occur throughout the summer, then regularly over a period of one to two years, gradually decreasing in the in 2021
Scenario 2: The first wave of Covid-19 is followed by a larger wave in the fall or winter and one or more smaller waves in 2021. “This model will require the reintroduction of mitigation measures to the “Fall to try to reduce the spread of infection and prevent health systems from being overwhelmed,” they wrote. “This pattern is similar to what was observed with the 1918-1919 pandemic.”
Scenario 3: a “slow combustion” of the transmission in progress. “This third scenario is unlikely to require the reinstatement of mitigation measures, although cases and deaths will continue to occur.”
States and territories should plan for scenario 2, the worst case scenario, they recommended.
“Government officials should develop concrete plans, including triggers to reinstate mitigation measures, to deal with peaks of disease when they occur,” they advised.
Lipsitch and Osterholm both said they were surprised by the decisions many states are taking to lift restrictions to control the spread of the virus.
“I think it’s an experience. It’s an experience that will likely cost lives, especially in places that do so without careful checks to try to figure out when to try to slow things down again,” said Lipsitch.
In addition, he said, some states choose to lift the restrictions when they have more new infections than they had when they decided to impose the restrictions.
“It’s hard to even understand the rationale,” said Lipsitch.
A vaccine could help, the report said, but not quickly. “The course of the pandemic could also be influenced by a vaccine; however, a vaccine is unlikely to be available until at least 2021,” they wrote.
“And we don’t know what kinds of challenges might arise during the development of a vaccine that could delay the timeline.”