Since the COVID-19 pandemic began a year and a half ago, there has always been a debate about how serious COVID-19 really is compared with common seasonal flu which kills tens of thousands each year. Even after more than 600,000 Americans have died and as cases are soaring again the hope is that the death rate in the USA will not be as bad now that half of all Americans have been fully vaccinated.
The coincident death rate (daily deaths divided by daily new cases) allows us to gauge how deadly a disease is but it has several shortcomings principally due to the fact that deaths lagged infections by a couple of weeks as hospitals and doctors struggle to save patients’ lives. As reported death counts have an additional problem since some counties and states take several weeks to fully record and report the cause of death. But since reported death rates are a convenient measure of disease severity and effectiveness of treatment we proposed to use a lagged case fatality rate (CFR = daily deaths divided by an infection curve weighted average of reported cases over the prior 4 weeks). This adjusted CFR is still just an estimate (since both case and death counts are widely believed to be undercounted), but it allows us to forecast future death counts and to assess whether hospitals and doctors were swamped and patients were unnecessarily lost due to poor planning and shortage of supplies (as they were during the early stages of the pandemic when this ratio was higher than 10% in the USA), and whether treatment methods have improved or not.
The CFR decreased significantly throughout 2020 even as the USA saw ever-larger surges in infections than the original one last spring. One major reason is that testing improved so more cases including mildly symptomatic and asymptomatic cases were identified (and the CFR denominator was better measured). Another is that more effective therapeutics and equipment became available and improved outcomes. A third reason is that more seniors more vulnerable to COVID-19 took precautions not to get infected and the average age of hospitalized patients declined.
Unfortunately, the progress seen in 2020 appears to have stalled in 2021 with CFR consistently near 1.8% even though the expectation is that the CFR should have improved further as vaccines became widely available.
- As vaccines were rolled out and made available primarily to frontline workers and seniors and those with comorbidities a large part of the vulnerable population should have been removed from the infection pool
- The average age of hospitalized patients continued to decline and the very strong CFR age effect should have driven the overall CFR down.
- Improved therapeutics became more widely available. While monoclonal antibodies were introduced last year, they were only available in limited quantities and that supply constraint should have eased in 2021.
Countering these positive trends were some negative ones:
- Many falsely believed that vaccinations protected them fully when the truth is that 95% protection is extremely good but not perfect. The vaccine made an 80yrs old male 10-20 times less likely to die – about the same vulnerability as an unvaccinated 60yrs old female with 1.5% mortality. More people letting down their guards may have contributed to keeping death rates high
- The new delta variant may be more lethal than the original. It is known to be 2.3 times as contagious but most scientists believe that it is not any more lethal though no one really knows yet.
- Easing or removal of many mitigation measures such as masking indoors in mid-May by the CDC which mostly impacted infection rates but may have increased viral loads transmitted as well
The lack of an improvement in CFR is extremely disappointing and troublesome. In the UK where there were more mitigation measures in place to protect the unvaccinated and slow the spread, a significant portion of the infections were breakthrough cases with lower fatality rates helping to bring their overall CFR down. With the removal of nearly all mitigation measures on 7/19/21 more of the UK infection pool will be the unvaccinated (plus vaccinated but immunocompromised) who will suffer higher fatality rates worsening overall CFR for the UK.
In the USA, most states removed their mitigation measures this spring so the infection pool remained dominated by the unvaccinated and the CFR has remained high. We are forecasting that 8,000 Americans will die over the next 4 weeks due to cases and hospitalizations already in the queue. About 400 of these will be “breakthrough” deaths of fully vaccinated people. We are forecasting a modest improvement in the USA CFR to 1.5% as masking is reintroduced. Nevertheless, this fifth wave could be nearly as deadly as the previous two and kill tens of thousands of Americans unnecessarily.