The omicron variant is more contagious and more vaccine-invasive than previous variants of Covid-19. When omicron began to surge in the United States, we wondered whether it would have a similar trajectory to the delta surge. There have been some key differences—including both bad and good news. We dug into the data to analyze the impact that vaccination rates will have on surges in hospitalization.
The bad news first: It doesn't look like a higher vaccination rate offers ample protection against an omicron surge.
Nearly every state has experienced a lasting Covid-19 surge since December 2021, regardless of vaccination rate. (It's a good time to live in Alaska.) Furthermore, higher vaccination rates haven't brought down the number of days in surge, with an average surge time hovering around 20 days.
Three factors explain the difference. Omicron is more contagious than previous variants of the virus, is more able to avoid immunity, and arrived in winter. The booster vaccine should offer improved immunity and protection against hospitalization, but rates are likely too low to meaningfully inflect hospitalizations at this point, ranging between 10% and 39% across states according to our analysis of CDC data.
The good news: States with higher vaccination rates have experienced fewer days in intense surges.
This is true when Covid-19 patients occupy more than 20% of hospital beds in the state. So far, states with vaccination rates above 60% that experience an intense surge have spent an average nine days at that level. States with vaccination rates below 60% spent an average of 16 days.
That aligns with early evidence that suggests that a two-dose vaccine course offers meaningful protection against hospitalization.
Even in states with lower vaccination rates, there's hope that the omicron wave will be shorter than delta, though still more intense than in states with higher vaccination rates. By January 9, no state had gone more than nine days with more than 30% of hospital beds occupied by patients with Covid-19. During the delta wave, Florida and Georgia both spent 25 days at that peak intensity.
Looking at hospitalization rates alone may overstate the severity of the omicron wave. With a more contagious but milder infection, more patients are testing positive with the virus even if they aren't hospitalized because of the virus. Furthermore, patients hospitalized for Covid-19 caused by the omicron variant show lower length of stay, which might mitigate the impact of a higher hospitalization rate.
But with a clinical workforce plagued by burnout and stretched to the limit, even a “smaller” surge in hospitalizations places an outsized burden on the health care system. That’s especially true now; staff shortages have led to closures in non-hospital settings, pushing more patients to seek care at hospitals. At the same time, staff shortages leave nursing homes at capacity, leading to discharge delays that keep patients in the hospital for longer and constrain capacity.
Furthermore, the delta variant is still prevalent in parts of the country. As a result, some states might see more intense surges that mix both the higher numbers of patients with the omicron variant and the higher likelihood of hospitalization for patients with the delta variant. That mix could also extend the duration of the surge, with the omicron variant driving up case numbers as the delta variant fades in prevalence.
Based on this early analysis, we would speculate that states with vaccination rates above 60% should expect elevated hospitalizations for Covid-19 for the duration of the wave, but intense surges with over 20% of hospital beds occupied by patients with Covid-19 for about two weeks.
For states with vaccination rates under 60%, those intense surges are likely to last longer.
Across the country, staffing shortages are likely to make intense surges more difficult to manage than they were during the delta wave.
Update on January 25: We returned to this analysis with two additional weeks of data and found that our main insight—that states with higher vaccination rates saw shorter intense surges—has changed. The new analysis shows them almost at parity: 17 days on average for states with lower rates, 19 days on average for states with higher rates.
We think that’s probably a matter of timing. States with higher vaccination rates were more likely to be hit earlier, and therefore have experienced more days in surge in an ongoing wave. We expect that the average will be even closer as later-hit states, which also often have lower vaccination rates, reach their peak rate of beds occupied by patients with Covid-19.
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