HomeMy WebLinkAboutvaccine-preventable-disease-fact-sheet-2019-2023-adaVaccine-Preventable Diseases in Alameda County, 2019-2023
Disease Number
of Cases
5-year Case Rate
(per 100,000)
Percent of Cases
Known to be Vaccinated
Pertussis 123 7.97 88%
Mumps 20 1.3 60%
Haemophilus influenzae*8 0.52 63%
Invasive Meningococcal Disease <5 —33%
Diphtheria <5 —100%
Tetanus <5 ——
Measles 0 0 —
Rubella 0 0 —
Total 156 10.1 —
Background
Medical providers in California are required to report cases of vaccine-preventable diseases to
the local public health department as specified by Title 17 of the California Code of Regulations.
This fact sheet summarizes confirmed, probable, and suspect cases of: invasive meningococcal
disease, diphtheria, mumps, rubella, Haemophilus influenzae, measles, pertussis, and tetanus
from 2019—2023.
Case Counts and Rates
One-hundred fifty-six cases of vaccine-preventable diseases were reported in Alameda County
from 2019-2023. The majority of cases (79%) reported were pertussis, followed by mumps (13%)
and H. influenzae (5%, Table 1). None of the H. influenzae cases were serotype B.
Pertussis had the highest case rate, with 7.97 cases per 100,000 people over a 5-year period. No
cases of measles or rubella were reported during this timeframe. In 2019 there were 16
exposure events to out-of-jurisdiction measles cases, resulting in 102 Alameda County contacts
investigated during this time period. No contacts became cases.
Table 1. Vaccine-Preventable Disease 5-year Rates and Counts
*Only reportable in those < 5 years old
1
Vaccine-Preventable Diseases in
Alameda County, 2019-2023
Case Demographics
Hispanic and Latino/a/x/e residents had the highest percent and case rate of vaccine-preventable
diseases. The majority of vaccine-preventable disease cases were among children ages 6-18 years
old (51%), and most of the cases in this age group were pertussis (95%).
Case rates were highest among children less than one year of age, with a rate of 101.7 cases per
100,000 infants over a five-year period (Table 2). The majority of these cases were pertussis (61%)
and H. influenzae (21%). Almost two-thirds (63%) of the infant pertussis cases had mothers who
were not known to have received the vaccine during pregnancy.
Table 2. Demographics of Vaccine-Preventable Disease Cases, 2019—2023
Demographic Category Cases Percent 5-Year Case Rate per 100,000
Age Group <1 yrs 18 12%101.7
1-5 yrs 34 22%36.6
6-18 yrs 79 51%31.5
19-59 yrs 21 13%2.5
60+ yrs < 10 ——
Race/Ethnicity African American or Black 10 6.4%6.6
Asian 35 22%7
Hispanic or Latino/a/x/e 42 27%11.8
Multiracial < 10 ——
Pacific Islander < 10 ——
White 29 19%6.5
Other/ Unknown 35 22%—
Gender Female 83 53%10.6
Male 73 47%9.6
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Table 3. Epidemiologic and Clinical Characteristics of Vaccine-Preventable Disease
Cases, 2019-2023
Vaccine-Preventable Diseases in
Alameda County, 2019-2023
Clinical Characteristics and Epidemiology -
Pertussis
Among pertussis cases, no patients died, and only one
was hospitalized; 88% of pertussis cases were immunized
for the disease (Table 3). Of these cases, 46% of those
with a date on record had been vaccinated 3 or more
years prior to disease onset. Immunity to pertussis is
known to wane by the next booster, and 41% of
vaccinated cases were between the ages of 13-18 years
old. Outbreaks in schools among this age group often
occur. The reason for outbreaks of pertussis despite high
vaccination rates remains unknown; however, for this age
group timeliness of testing may have contributed to
transmission in school/childcare settings. The average
number of days between symptom onset and testing was
18 days. The average number of days between onset and
treatment was 19 with a minimum of 7 days between
onset and treatment recorded. It is important to note that
there was only one hospitalization for pertussis during
this 5 year time period, highlighting the effectiveness of
the vaccine in preventing severe disease. Of the seven
pertussis cases that were unvaccinated, the most
common reasons were personal belief exemptions.
Clinical Characteristics and
Epidemiology - Other Diseases
Among the other disease cases, no
patients died, 12 (36%) were
hospitalized, and two were
immunocompromised. Only 57% of
these cases were known to be
immunized against the disease. Being
under the recommended age of
vaccination was the most common
reason for not being vaccinated (75%).
Among mumps cases, only 5 (25%) had
buccal PCR tests and none had paired
acute and convalescent IgG testing.
Meanwhile, 11 (55%) cases had mumps
serum IgM tests collected, which was
the only test for nine of these cases. For
the eight cases with parotitis that were
tested by IgM only, all were tested
within 9 days of swelling onset,
highlighting a missed opportunity for
PCR testing, which can occur up to 10
days after parotitis onset.
Epidemiologic and Clinical Characteristics Pertussis Cases
N = 123
All Other Disease Cases
N = 33
Immunocompromised 0 (0%)2 (6.1%)
Hospitalized 1 (0.8%)12 (36%)
Died 0 (0%)0 (0%)
Travel During Incubation Period 6 (4.9%)5 (15%)
Immunized for Disease 108 (88%)18 (55%)
Unknown Immunization Status 8 (6.5%)11 (33%)
Not Immunized for Disease 7 (5.7%)4 (12%)
Not vaccinated due to - under age for vaccination 0 (0%)3 (9.1%)
Not vaccinated due to - Personal Beliefs Exemption 3 (2.4%)0 (0%)
Not vaccinated due to - Permanent Medical Exemption 2 (1.6%)0 (0%)
Not vaccinated due to - Delay in series 2 (1.6%)0 (0%)
Not vaccinated due to - Unknown 3 (2.4%)1 (3%)3
Vaccine-Preventable Diseases in
Alameda County, 2019-2023
For questions or additional information, contact:
Alameda County Public Health Department
Acute Communicable Diseases Section
https://health.alamedacountyca.gov/pr
ogram/acute-communicable-diseases/
Last updated April 7th 2026
Kindergarten Vaccination Rates in Alameda County
While Alameda County generally has higher Kindergarten vaccination rates than the state as a whole,
vaccination coverage decreased during the COVID-19 pandemic, and remained lower than pre-
pandemic years (Figure 1).
Figure 1. Kindergarten Vaccine Coverage in Alameda County, 2019-2023
*Received all required
immunizations, including: 5 or
more of Diphtheria, Tetanus and
Pertussis (DTaP) vaccine (4 doses
are acceptable if at least 1 dose
was received on or after the
fourth birthday); 4 or more of
Polio vaccine (3 doses are
acceptable if at least 1 dose was
received on or after the fourth
birthday); 2 doses of Measles,
Mumps and Rubella (MMR)
vaccine or two doses of Measles,
two doses of Mumps, and one
dose of Rubella vaccine,
separately or combined, on or
after the first birthday; 3 or more
of Hepatitis B (Hep B) vaccine;
and 2 or more of Varicella.
Provider Recommendations
Over the five-year period, Alameda County had low case counts and rates of vaccine-preventable
diseases due to high vaccination coverage, as evidenced by Kindergarten vaccination rates.
Providers can use these data to emphasize the effectiveness of childhood vaccinations.
If mumps is suspected, the ideal sample for confirming diagnosis is a mumps PCR. Specimens
should be collected ideally within 3 days post-onset of parotitis, but can be collected up to 10 days
after onset. Please refer to this flow chart for healthcare providers.
Timely testing and treatment of pertussis cases can prevent transmission, protect high-risk
individuals such as infants, and prevent outbreaks in school/childcare settings. The preferred
method for the diagnosis of pertussis is PCR. Healthcare providers should test patients within the
first 3 weeks of cough onset.
It is recommended that pregnant persons receive the Tdap vaccine during pregnancy. Evidence
shows that infants are less likely to develop pertussis early in life if their mother received Tdap
during pregnancy.
It is still important to encourage childhood vaccinations and address misinformation and
disinformation.
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