COVID-19 Hospitalizations and Deaths by Vaccination Status in

COVID-19 Hospitalizations and Deaths

by Vaccination Status in Washington

State

Washington State Department of Health

December 12, 2023

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please call 711 (Washington Relay) or email civil.rights@doh.wa.gov.

Publication Number: 421-010

For more information or additional copies of this report:

Division of Prevention and Community Health

Office of Immunization

111 Israel Rd SE

Tumwater, WA 98501

Phone: 360-236-3595

Email: WAIISDataR[email protected]

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COVID-19 Hospitalizations and Deaths by Vaccination Status in

Washington State

December 12, 2023

PLEASE NOTE: information about bivalent booster doses (authorized in the fall of 2022) or the updated

monovalent booster doses (authorized in September of 2023) is not included in this report.

Summary

From November 02 to November 29, 2023, unvaccinated individuals were

between 1.6 and 7.2 times more likely to be hospitalized with COVID-19

compared to those who received at least one booster dose*

From October 11 to November 07, 2023, unvaccinated individuals were

between 1.8 and 3.9 times more likely to die from COVID-19 compared to those

who received at least one booster dose*,**

*Booster here includes additional doses or monovalent booster doses (excluding bivalent booster doses

authorized on September 1, 2022)

**Due to a small number of COVID-19 deaths, death rates in certain age groups may be unstable.

Resulting rate ratios should be interpreted with caution.

Background

Vaccination is an important tool for controlling the COVID-19 pandemic. COVID-19 vaccines are safe and

effective at reducing the risk of severe infections, being hospitalized, and dying from COVID-19.

Approximately 70% of the Washington population ages 6 months and older has completed the primary

COVID-19 vaccine series and over half of the population has received at least one booster dose (shot).

Unvaccinated Washingtonians are at risk of serious outcomes such as being hospitalized and dying due

to COVID-19. Because vaccination rates vary across the state between different age and demographic

groups, some populations may be more vulnerable to these serious outcomes.

Although COVID-19 vaccines work well to protect against severe infections, being hospitalized, and

dying from COVID-19, some people who are vaccinated with the primary series or who have received a

booster dose will still get COVID-19 if they are exposed to the virus. As more individuals become

vaccinated it is natural to see more vaccinated individuals get COVID-19, and even be hospitalized or die

from COVID-19. However, because people who have completed the primary series and received at least

one booster dose are much less likely to be hospitalized or die compared to those who are

unvaccinated, increasing vaccination rates remains important to protect Washingtonians from severe

COVID-19 infections and save lives.

This report shows the impact of vaccination on COVID-19 in Washington by describing rates of COVID-19

hospitalizations and deaths among people with different vaccination statuses. This report breaks

vaccination status into three categories:

• Unvaccinated: those who have not received any dose of an authorized COVID-19 vaccine.

• Completed primary series: those who have reached two weeks after receiving the final

recommended dose of the primary series of an authorized COVID-19 vaccine.

• Boosted: those who have reached two weeks after receiving at least one booster dose or

additional dose of a monovalent COVID-19 vaccine. Individuals are not considered to have full

protection from the monovalent booster dose until two weeks have passed since receiving the

dose because of the time required for the body to build protection. COVID-19 vaccines

categorized as “monovalent” are the initial COVID-19 vaccines that were approved by the Food

and Drug Administration (FDA). Doses used for the primary series are monovalent vaccines.

These are different from the new booster doses authorized by the FDA for use beginning

September 1, 2022, which are referred to as “bivalent” vaccines. Data about doses of bivalent

boosters are not included in this report.

PLEASE NOTE:

• Information about bivalent boosters is not included in this report in order to avoid confusing the

impact of the bivalent boosters with the impact of the monovalent boosters. Individuals who

received a bivalent booster after August 31, 2022 are removed from the analyses presented

here. Information about the impact of bivalent boosters will be included in future iterations of

this report once a sufficient percentage of the Washington population has received the booster.

• Immunocompromised individuals are eligible for an additional dose following the primary series

before being eligible for a booster dose. Because DOH has very limited data about whether

someone is immunocompromised, all doses received after the primary series is completed are

categorized as “booster doses”.

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Impact of vaccination on COVID-19 hospitalization and death rates

The following graphs show the 28-day COVID-19 hospitalization and death rates by age group for people

with different vaccination statuses. There are several important things to know when looking at the

data. First, individuals who have received at least one booster dose (represented by the blue line in the

following graphs) are less likely to be hospitalized or die of COVID-19 compared to those who are

unvaccinated (red line) as well as those who completed the primary series (yellow line). However,

because even very effective vaccines cannot prevent all infections, some individuals who have received

at least one booster dose may still get sick, be hospitalized with, or die from COVID-19. There may also

be other reasons these individuals experience serious outcomes even after receiving at least one

booster dose, including:

• Decreasing protection from the vaccine as more time passes from when individuals received

their most recent dose

• The spread of variants that are more contagious and that current vaccines are not as protective

against

• Individuals and society changing behaviors such as masking, social distancing, and seeking

testing

Interpreting the data is challenging because of several factors that are hard to measure in the

population, including:

• The number of unvaccinated individuals with some protection from COVID-19 because of a

previous infection

• The use of at-home tests and information about people who test positive not being reported to

the Washington State Department of Health

• Individuals with underlying health conditions potentially being more likely to both get

vaccinated and boosted, and also experience severe outcomes from COVID-19

• The potential for people who are vaccinated and boosted to be more likely to be tested

These limitations have a larger impact on case data compared to hospitalization and death data and

have also become more relevant in recent months. Therefore, case data are no longer included in this

report.

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Trends in COVID-19 hospitalization and death rates by vaccination status and

age group

The following graphs show the 28-day COVID-19 hospitalization and death rates by age group for people

who are unvaccinated, people who have completed the primary series, and people who have received at

least one booster dose. The difference between rates in the unvaccinated population compared to the

population of those who have received at least one booster dose during the grayed out 28-day time

period is shown in text on each graph.

PLEASE NOTE: the Y-axes of the following graphs differ between age groups.

COVID-19 Hospitalizations

COVID-19 hospitalization rates per 100,000 population by age and vaccination

status, November 02 to November 29, 2023

Age group

Age-specific rate

per 100,000 among

unvaccinated

individuals

Age-specific rate

per 100,000 among

those who received

at least one booster

dose

Likelihood of unvaccinated

individuals being hospitalized with

COVID-19 compared to those who

received at least one booster dose

5 - 11

Not calculated*

12 - 34

7.9

1.1

7.2

35 - 64

16.3

5.3

3.1

65+

94.1

58.7

1.6

*Rates are not calculated when there are five or fewer hospitalizations in either the unvaccinated or

boosted group. The underlying number of hospitalizations is too small to analyze and draw meaningful

conclusions about the impact of booster doses on hospitalizations.

COVID-19 hospitalization rates among 5 - 11 year-olds were low across all

vaccination statuses*

*The rate ratio is not included on this graph because the underlying number of hospitalizations is too

small to analyze and draw meaningful conclusions about the impact of booster doses on hospitalizations

in this age group

COVID-19 hospitalization rates among 12 - 34 year-olds are 7.2 times higher in

the unvaccinated population than in the population receiving at least one

booster

COVID-19 hospitalization rates among 35 - 64 year-olds are 3.1 times higher in

the unvaccinated population than in the population receiving at least one

booster

COVID-19 hospitalization rates among 65+ year-olds are 1.6 times higher in the

unvaccinated population than in the population receiving at least one booster

COVID-19 Deaths

Deaths are only shown for Washingtonians ages 35 years and older due to the relatively small number of

deaths in other age groups and associated instability in rates when assessing by vaccination status.

COVID-19 death rates per 100,000 population by age and vaccination status,

October 11 to November 07, 2023

Age group

Age-specific rate

per 100,000 among

unvaccinated

individuals

Age-specific rate

per 100,000 among

those who received

at least one booster

dose

Likelihood of unvaccinated

individuals dying from COVID-19

compared to those who received

at least one booster dose

35 - 64

0.5

0.1

3.9

65+

12.2

6.9

1.8

COVID-19 death rates among 35 - 64 year-olds are 3.9 times higher in the

unvaccinated population than in the population receiving at least one booster

COVID-19 death rates among 65+ year-olds are 1.8 times higher in the

unvaccinated population than in the population receiving at least one booster

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Methods

Data sources

There are three data sources for these metrics:

• Washington Disease Reporting System (WDRS)

• Washington Immunization Information System (WAIIS)

• Washington Health and Life Events System (WHALES)

WDRS receives case, hospitalization, and death information for all COVID-19 cases in Washington

residents reported to the Washington State Department of Health. WAIIS collects COVID-19 vaccination

data from healthcare providers for people vaccinated in Washington, as well as Washington residents

vaccinated outside of the state. Not all federal correction facilities and federal healthcare organizations

(e.g., Department of Defense and Veterans Administration facilities) submit data to WAIIS. WAIIS may

not include vaccination data from all tribal health facilities.

All rates presented in this report are calculated using the Washington state population distribution

based on the Office of Financial Management’s (OFM) April 1, 2020 population estimates. To better

reflect the true rates of COVID-19 hospitalizations and deaths in this report, calculations include only the

5 years and older population because they were eligible to receive booster doses during the assessment

period.

Definitions

All case, hospitalization, and death data reported are based on positive molecular or antigen test results.

A person classified as a COVID-19 case who received at least one booster dose is defined as a person

with a positive molecular or antigen test result and a specimen collection date two or more weeks after

their first booster dose of a monovalent COVID-19 vaccine is administered. An individual is considered to

have received a booster dose two weeks after an age-appropriate booster dose is administered.

A COVID-19 hospitalization is a hospitalization of a Washington resident with COVID-19 who has been

identified using case investigation data in WDRS or links with Rapid Health Information Network (RHINO)

records as hospitalized with confirmed or probable COVID-19.

Deaths are reported to the state by health care providers, medical examiners or coroners, local health

departments, or others to the official vital records database, WHALES. COVID-19 deaths included in this

report are identified in WHALES where the cause of death was confirmed or suspected to have been

COVID-19, and require a known positive test result.

Timeframes

It takes up to 10 days from specimen collection date for DOH to receive information about 90% of

reported cases, 10 days for DOH to identify hospitalizations, and 32 days to identify deaths. For this

reason, we report time periods differently for hospitalizations and deaths to ensure we are reporting the

most complete data.

Linking methods

All information on COVID-19 cases, hospitalizations, and deaths in this report use WDRS data linked to

WAIIS COVID-19 vaccination data. The method to link data was updated in July 2022 to include more

robust linking methods. The links are based on a comparison of the following demographic information

present in both WDRS and WAIIS:

• first name

• last name

• middle initial

• date of birth

• sex at birth

• phone number

• zip code

The new methodology identifies matches even when there are slight variations in the spelling of names

or small errors in other demographic information between the two data sources. This method is a more

robust method of linking data than the previous method, which required exact matches of first name,

last name, and date of birth for records to be considered a match. COVID-19 cases with vaccines not

reported to WAIIS as described above are considered unvaccinated in this report.

28-day rate calculations

Rates are calculated as the total number of hospitalizations or deaths within the specified vaccination

and age groups with a specimen collection date during the 28-day period divided by the population that

falls in the same age group with the same vaccination status at the beginning of the 28-day period.

For example,

28-day COVID-19 hospitalization rates per 100,000 population among 12 - 34 year-old individuals who

received at least one booster dose =

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To compare rates in the population of individuals who received at least one booster dose to the

unvaccinated population, the rates for the most recent four-week (i.e., 28-day) period is calculated. The

28-day rate in the unvaccinated population is divided by the 28-day rate in the population of individuals

who received at least one booster dose to calculate a rate ratio.

For example,

The rate ratio for the boosted and unvaccinated COVID-19 hospitalization rates per 100,000 population

among 12 - 34 year-old individuals on August 28 =