RESULTS
From March 1, 2020 to January 2, 2021, nationally for all ages combined,
all-cause mortality was in the very high severity category for 9 weeks,
from weeks 15 through 17 (April 5-April 25) and weeks 48 through 53
(November 22, 2020- January 2, 2021) (Figures 1-2). Forty-seven states,
the District of Columbia, and New York City each experienced at least
one very high severity week for all ages combined (Figure 2). The
average number of very high severity weeks per jurisdiction was 7.5
weeks, about 17% of the period from week 10 to week 53. There was
variation in when states experienced very high severity and for how
long. Overall, there were three distinct periods in which individual
states experienced very high severity, in the spring during weeks 13-22
(March 22-May 30), in the summer from weeks 27-35 (June 28-August 29)
(Figure 2), and in the fall/winter from weeks 41-53 (October 4-January
2). Some states experienced very high severity in multiple time periods,
although most states did not experience very high severity until the
fall/winter weeks. Hawaii, Maine, and Washington had no weeks of very
high severity; Alaska, New Hampshire, Oregon, and Vermont had only one
week.
Among children under 18 years old, all-cause mortality was of moderate
severity for week 28; all other weeks were low severity weeks for this
age group; and none of the weeks were high or very high severity. All
the adult age groups experienced some weeks of very high severity,
though the number of weeks decreased with increasing age group, with 29
weeks of consecutive very high severity among adults 18 to 49 years old
(Figure 3). Supplemental figures display time series for age groups
(Figures S1-S6).
Supplemental figures illustrate the adjustment for secular trend (Figure
S7), the values used to compute the ITs (Figure S8), and the statistical
assumptions about the categories of severity (Figure S9).