Data prep

COVID-19 breakthrough cases among Harford County residents in Maryland - summary

(Page updated at 2022-02-24 20:39:53)
See annex at the end for data sources. For further data analysis, methods, and detailed note on data sources, please see the full note here.

1. What are the level and trend of breakthough cases?

  1. To date, among people who have been fully vaccinated in the county (n=154890), 5986 breakthrough cases have been reported.
  2. This means 3.9% have had a breakthrough case - assuming no multiple breakthrough cases per person.
  3. After the peak in early January, the level is now similar to mid-December level.

2. What is the risk of having COVID-19 among fully vaccinated people vs. non-fully vaccinated people?

At the peak in early January, the rate of reported new infection was more than 10 times higher among non-fully vaccinated people than among fully vaccinated people (7-day new cases per 100,000 population: ~3500 vs. ~300).

This simple breakdown suggest the current surge is driven by cases among non-vaccinated people.

(Note: the number of fully vaccinated people is set stable since December 3, due to the Immunet data access transition. This mean, the rate among fully vaccinated people might have been slightly lower than the calculated above, as the vaccination rate has increased slightly/gradually since early December.)

3. Have characteristics and outcome of breakthrough cases changed over time?

Note: people with breakthrough cases tend to be older than people who have cases without being fully vaccinated.

For example, in Maryland, 27% of people with breakthrough cases are 60 or older in the last 60 days. But, among all people with COVID, 19% were 60+ in the last 30 days and 14% in the previous 30 days. This explains why the cumulative case fatality ratio among breakthrough cases is not as low as one may expect. FYI, in Maryland, cumulative case fatality ratio is 1.4% during the pandemic.

COVID-19 breakthrough cases by group: prior to vs. during the last 60 days
Group Group.label in the last 60 days: Harford county, Number in the last 60 days: Harford county, % in the last 60 days: MD, Number in the last 60 days: MD, % Prior to the last 60 days: Harford county, Number Prior to the last 60 days: Harford county, % Prior to the last 60 days: MD, Number Prior to the last 60 days: MD, %
By Age
11 and Under 268 6 6644 6 9 0 515 1
12-19 275 7 7566 7 141 8 4570 10
20-29 459 11 14698 13 235 13 7496 17
30-39 723 17 18982 17 369 20 8398 19
40-49 685 16 17543 16 289 16 7245 17
50-59 648 16 17506 16 302 17 6875 16
60-69 588 14 14852 13 254 14 5044 12
70+ 534 13 13367 12 207 11 3559 8
By death
No 4132 98.9 110074 99 1793 99.3 43500 99.5
Yes 48 1.1 1084 1 13 0.7 202 0.5
By hospitalization
No 3854 92.2 103031 92.7 1747 96.7 42612 97.5
Yes 326 7.8 8127 7.3 59 3.3 1090 2.5
By Having.Symptoms
missing 3259 78 84714 76 792 44 21228 49
No 118 3 4184 4 425 24 7679 18
Yes 803 19 22260 20 589 33 14795 34
By Congregate.Housing
0 4112 98.4 108164 97.30654 1778 98.4 43212 98.9
1 68 1.6 2994 2.69346 28 1.6 490 1.1

4. Among Harford county residents who were hospitalized, what are their vaccination status?

  • In the last two months, among 60+ COVID-19 admission cases (dark blue + red blue), 60% were breakthrough cases (dark blue).
  • As of early December, 87% of 65+ were fully vaccinated. 73% of 40-65 were fully vaccinated.
  • Hospital case data from MDH have vaccination information only for the first two doses. Thus, booster status cannot be determined using the data.