But this current surge is different. The approval of three highly effective vaccines in the United States that significantly reduce severe disease and transmission has indeed brought a new sense of hope that we can return to normalcy soon. There is no doubt that vaccines will help bring an end to the acute, emergency phase of this pandemic and usher us into endemicity, which is when covid-19 would be like any other respiratory infection that we could live with. In the short term, though, vaccines alone are not preventing a rebound of infections as more than two dozen states are currently facing. Of note, the same thing happened in Israel as its vaccine rollout began, with a rebound in cases at first until they plummeted after 40 percent of first doses of vaccine were provided. The states where cases are surging will need pandemic control measures to tamp down transmission, since only 32.6 percent of the U.S. population has received their first dose, and just 19 percent of us are fully vaccinated.
To get through this next stage of the pandemic as safely as possible, we’ll need to know when we can lift restrictions without sparking new surges. Fortunately, if we pay attention to some key metrics, we can figure that out.
A recent British mathematical modeling study showed that even a vaccine that’s 85 percent effective in preventing infection is still not enough to drive the reproductive rate of the virus (an indicator that shows if the epidemic is growing) below 1 without some ongoing nonpharmaceutical (NPI) measures — such as restrictions on businesses, mask requirements, etc. — as vaccines are being distributed. And if the rate is above 1, the epidemic will continue to spread. Real-world data show that vaccines do help, reducing the chances of asymptomatic transmission by somewhere from 80 percent to 94 percent in people who are fully immunized. But vaccination by itself will not be enough to stop the virus’s spread in places with high rates of transmission until a lot of people get vaccinated. That means that until we get there, there will be many unnecessary infections, hospitalizations and deaths among people who could have been just a few weeks away from being protected by the vaccine.
We’re all pandemic-weary, yearning to go back to life as we knew it before covid-19 took over. Hearing public health and elected officials warn of “impending doom” of another surge, and seeing governors, mayors and local leaders consider reinstating restrictions if their community shows increased cases is like living through Groundhog Day — the message is clearly needed, but when does it end?
The key is the gradual loosening of restrictions tied to high vaccination rates and low rates of severe disease, hospitalizations and death. But what are the rates at which we can safely lift restrictions? Many experts have indicated restrictions should be lifted when our hospitalizations and deaths from the coronavirus reach those similar to influenza, an infection for which we do not impose societal restrictions. But influenza leads to an average of 55 to 140 deaths a day in the United States. For covid-19, we’re currently seeing a seven-day moving average of 745 deaths a day. At this point, there is no threshold that has been set for what death rate is acceptable from covid-19, but we must make decisions as a society for what we can tolerate. (Other countries have used specific thresholds, such as the four-step Go-Slow Plan to take England out of lockdown by summer.)
As clinicians and epidemiologists, we see the tipping point at which restrictions like masks and social distancing can be lifted by looking at two parameters: 1) severe disease from covid-19 as represented by hospitalizations and 2) vaccination rates. The goal for hospitalizations from covid-19 should be less than 5 cases per 100,000 people, or about 16,000 hospitalizations in the nation, less than half of where we are right now. This is lower than the hospitalization rates from influenza during the height of the flu season, which normally shows an average of 20 to 40 hospitalizations per 100,000 people, but mortality for hospitalized covid patients remains very high. Further, the coronavirus vaccines are all much more effective than the current influenza vaccines. And as such, the Israeli experience suggests that once we manage to get at least 40 percent of people at least one dose, we can expect substantial and sustained drops in infection rates. Of course, this percentage will be influenced by other factors, such as the underlying rate of immunity from previous infections. It’s important to look at these quantitative numbers as key metrics for easing restrictions in each state. It will be a gradual process based on data, not dates. States will need to continue to be nimble and vary restrictions accordingly during this transition phase of vaccine rollout.
It may seem as though we’re a desperately long way off from meeting these benchmarks: We currently clock in over 63,000 cases per day, 10.5 hospitalizations per 100,000 and a seven-day average of 745 deaths. However, some states are already approaching these metrics. Hawaii, New Mexico, Montana and Wyoming currently have fewer than five covid-19 hospitalizations per 100,000, and California (at 6.2 hospitalizations per 100,000) is at the lowest rate of the big states. If each state continues to have high vaccine uptake and distribution, we can end the emergency phase of this pandemic soon. In fact, 76 percent of adults aged 65 and up have already received at least one shot, and a majority (56.6 percent) are fully vaccinated. This is the group that made up a vast majority of severe cases, hospitalizations and death from covid-19 until very recently. Eight in 10 deaths reported from the virus before the vaccine rollout began were among senior citizens. The hospitalizations and deaths in this group are now plummeting.
All pandemics end. The question is, how do we know when they do? These metrics will help us know when to begin to lift restrictions and get on track to a new normal.