Estimating county-level vaccination coverage using small area estimation with the National Immunization Survey-Child.

The National Immunization Survey-Child (NIS-Child) provides annual vaccination coverage estimates in the United States for children aged 19 through 35 months, nationally, for each state, and for select local areas and territories. There is a need for vaccination coverage estimates for smaller geographic areas to support local authority planning and identify counties with potentially low vaccination coverage for possible further intervention. We describe small area estimation methods using 2008-2018 NIS-Child data to generate county-level estimates for children up to two years of age born 2007-2011 and 2012-2016. We applied an empirical best linear unbiased prediction method to combine direct estimates of vaccination coverage with model-based prediction using county-level predictors regarding health and demographic characteristics. We review the predictors commonly selected for the small area models and note multiple predictors related to barriers to vaccination.

COVID-19 Bivalent Booster Vaccination Coverage and Intent to Receive Booster Vaccination Among Adolescents and Adults - United States, November-December 2022.

COVID-19 vaccine booster doses are safe and maintain protection after receipt of a primary vaccination series and reduce the risk for serious COVID-19-related outcomes, including emergency department visits, hospitalization, and death (1,2). CDC recommended an updated (bivalent) booster for adolescents aged 12-17 years and adults aged ≥18 years on September 1, 2022 (3). The bivalent booster is formulated to protect against the Omicron BA.4 and BA.5 subvariants of SARS-CoV-2 as well as the original (ancestral) strain (3). Based on data collected during October 30-December 31, 2022, from the National Immunization Survey-Child COVID Module (NIS-CCM) (4), among all adolescents aged 12-17 years who completed a primary series, 18.5% had received a bivalent booster dose, 52.0% had not yet received a bivalent booster but had parents open to booster vaccination for their child, 15.1% had not received a bivalent booster and had parents who were unsure about getting a booster vaccination for their child, and 14.4% had parents who were reluctant to seek booster vaccination for their child. Based on data collected during October 30-December 31, 2022, from the National Immunization Survey-Adult COVID Module (NIS-ACM) (4), 27.1% of adults who had completed a COVID-19 primary series had received a bivalent booster, 39.4% had not yet received a bivalent booster but were open to receiving booster vaccination, 12.4% had not yet received a bivalent booster and were unsure about getting a booster vaccination, and 21.1% were reluctant to receive a booster. Adolescents and adults in rural areas had a much lower primary series completion rate and up-to-date vaccination coverage. Bivalent booster coverage was lower among non-Hispanic Black or African American (Black) and Hispanic or Latino (Hispanic) adolescents and adults compared with non-Hispanic White (White) adolescents and adults. Among adults who were open to receiving booster vaccination, 58.9% reported not having received a provider recommendation for booster vaccination, 16.9% had safety concerns, and 4.4% reported difficulty getting a booster vaccine. Among adolescents with parents who were open to getting a booster vaccination for their child, 32.4% had not received a provider recommendation for any COVID-19 vaccination, and 11.8% had parents who reported safety concerns. Although bivalent booster vaccination coverage among adults differed by factors such as income, health insurance status, and social vulnerability index (SVI), these factors were not associated with differences in reluctance to seek booster vaccination. Health care provider recommendations for COVID-19 vaccination; dissemination of information by trusted messengers about the continued risk for COVID-19-related illness and the benefits and safety of bivalent booster vaccination; and reducing barriers to vaccination could improve COVID-19 bivalent booster coverage among adolescents and adults.

Celebrating 25 Years of Varicella Vaccination Coverage for Children and Adolescents in the United States: A Success Story.

Tracking vaccination coverage is a critical component of monitoring a vaccine program. Three different surveillance systems were used to examine trends in varicella vaccination coverage during the United States vaccination program: National Immunization Survey-Child, National Immunization Survey-Teen, and immunization information systems (IISs). The relationship of these trends to school requirements and disease decline was also examined. Among children aged 19-35 months, ≥1 dose of varicella vaccine increased from 16.0% in 1996 to 89.2% by the end of the 1-dose program in 2006, stabilizing around at least 90.0% thereafter. The uptake of the second dose was rapid after the 2007 recommendation. Two-dose coverage among children aged 7 years at 6 high-performing IIS sites increased from 2.6%-5.5% in 2006 to 86.0%-100.0% in 2020. Among adolescents aged 13-17 years, ≥2-dose coverage increased from 4.1% in 2006 to 91.9% in 2020. The proportion of adolescents with history of varicella disease declined from 69.9% in 2006 to 8.4% in 2020. In 2006, 92% of states and the District of Columbia (DC) had 1-dose daycare or school entry requirements; 88% of states and DC had 2-dose school entry requirements in the 2020-2021 school year. The successes in attaining and maintaining high vaccine coverage were paramount in the dramatic reduction of the varicella burden in the United States over the 25 years of the vaccination program, but opportunities remain to further increase coverage and decrease varicella morbidity and mortality.

Human Papillomavirus Vaccination Trends Among Adolescents: 2015 to 2020.

OBJECTIVE: To assess trends in recent human papillomavirus (HPV) vaccination initiation and factors associated with vaccination among adolescents. METHODS: The 2015 to 2020 National Immunization Survey-Teen data were used to assess vaccination trends. Multivariable logistic regression analysis were conducted to assess factors associated with vaccination. RESULTS: Overall, HPV vaccination coverage (≥1 dose) among adolescents significantly increased from 56.1% in 2015 to 75.4% in 2020. There were larger increases in coverage among males (4.7 percentage points annually) than females (2.7 percentage points annually) and coverage differences between males and females decreased in 2015 through 2020. Coverage in 2020 was 75.4% for adolescents aged 13 to 17 years; 73.7% for males and 76.8% for females (P < .05); 80.7% for those with a provider recommendation and 51.7% for those without (P < .05); and 80.3% for those with a well child visit at age 11 to 12 years, and 64.8% for those without (P < .05). Multivariable logistic regression results showed that main characteristics independently associated with a higher likelihood of vaccination included: a provider recommendation, age 16 to 17 years, non-Hispanic Black, Hispanic, or American Indian or Alaskan Native, Medicaid insurance, ≥2 provider contacts in the past 12 months, a well-child visit at age 11 to 12 years and having 1 or 2 vaccine providers (P < .05). CONCLUSIONS: Overall, HPV vaccination coverage among adolescents increased during 2015 to 2020. Coverage increased faster among males than females and differences by sex narrowed during this time. Receiving a provider recommendation vaccination was important to increase vaccination coverage.

Vaccination Coverage by Age 24 Months Among Children Born in 2017 and 2018 - National Immunization Survey-Child, United States, 2018-2020.

Immunization is a safe and cost-effective means of preventing illness in young children and interrupting disease transmission within the community.* The Advisory Committee on Immunization Practices (ACIP) recommends vaccination of children against 14 diseases during the first 24 months of life (1). CDC uses National Immunization Survey-Child (NIS-Child) data to monitor routine coverage with ACIP-recommended vaccines in the United States at the national, regional, state, territorial, and selected local levels.† CDC assessed vaccination coverage by age 24 months among children born in 2017 and 2018, with comparisons to children born in 2015 and 2016. Nationally, coverage was highest for ≥3 doses of poliovirus vaccine (92.7%); ≥3 doses of hepatitis B vaccine (HepB) (91.9%); ≥1 dose of measles, mumps, and rubella vaccine (MMR) (91.6%); and ≥1 dose of varicella vaccine (VAR) (90.9%). Coverage was lowest for ≥2 doses of influenza vaccine (60.6%). Coverage among children born in 2017-2018 was 2.1-4.5 percentage points higher than it was among those born in 2015-2016 for rotavirus vaccine, ≥1 dose of hepatitis A vaccine (HepA), the HepB birth dose, and ≥2 doses of influenza vaccine. Only 1.0% of children had received no vaccinations by age 24 months. Disparities in coverage were seen for race/ethnicity, poverty status, and health insurance status. Coverage with most vaccines was lower among children who were not privately insured. The largest disparities between insurance categories were among uninsured children, especially for ≥2 doses of influenza vaccine, the combined 7-vaccine series, § and rotavirus vaccination. Reported estimates reflect vaccination opportunities that mostly occurred before disruptions resulting from the COVID-19 pandemic. Extra efforts are needed to ensure that children who missed vaccinations, including those attributable to the COVID-19 pandemic, receive them as soon as possible to maintain protection against vaccine-preventable illnesses.

COVID-19 Vaccination Coverage Among Adults - United States, December 14, 2020-May 22, 2021.

The U.S. COVID-19 vaccination program launched on December 14, 2020. The Advisory Committee on Immunization Practices recommended prioritizing COVID-19 vaccination for specific groups of the U.S. population who were at highest risk for COVID-19 hospitalization and death, including adults aged ≥75 years*; implementation varied by state, and eligibility was gradually expanded to persons aged ≥65 years beginning in January 2021. By April 19, 2021, eligibility was expanded to all adults aged ≥18 years nationwide.† To assess patterns of COVID-19 vaccination coverage among U.S. adults, CDC analyzed data submitted on vaccinations administered during December 14, 2020-May 22, 2021, by age, sex, and community-level characteristics. By May 22, 2021, 57.0% of persons aged ≥18 years had received ≥1 COVID-19 vaccine dose; coverage was highest among persons aged ≥65 years (80.0%) and lowest among persons aged 18-29 years (38.3%). During the week beginning February 7, 2021, vaccination initiation among adults aged ≥65 years peaked at 8.2%, whereas weekly initiation among other age groups peaked later and at lower levels. During April 19-May 22, 2021, the period following expanded eligibility to all adults, weekly initiation remained <4.0% and decreased for all age groups, including persons aged 18-29 years (3.6% to 1.9%) and 30-49 years (3.5% to 1.7%); based on the current rate of weekly initiation (as of May 22), younger persons will not reach the same levels of coverage as older persons by the end of August. Across all age groups, coverage (≥1 dose) was lower among men compared with women, except among adults aged ≥65 years, and lower among persons living in counties that were less urban, had higher social vulnerabilities, or had higher percentages of social determinants of poor health. Continued efforts to improve vaccination confidence and alleviate barriers to vaccination initiation, especially among adults aged 18-49 years, could improve vaccination coverage.

Disparities in COVID-19 Vaccination Coverage Between Urban and Rural Counties - United States, December 14, 2020-April 10, 2021.

Approximately 60 million persons in the United States live in rural counties, representing almost one fifth (19.3%) of the population.* In September 2020, COVID-19 incidence (cases per 100,000 population) in rural counties surpassed that in urban counties (1). Rural communities often have a higher proportion of residents who lack health insurance, live with comorbidities or disabilities, are aged ≥65 years, and have limited access to health care facilities with intensive care capabilities, which places these residents at increased risk for COVID-19-associated morbidity and mortality (2,3). To better understand COVID-19 vaccination disparities across the urban-rural continuum, CDC analyzed county-level vaccine administration data among adults aged ≥18 years who received their first dose of either the Pfizer-BioNTech or Moderna COVID-19 vaccine, or a single dose of the Janssen COVID-19 vaccine (Johnson & Johnson) during December 14, 2020-April 10, 2021 in 50 U.S. jurisdictions (49 states and the District of Columbia [DC]). Adult COVID-19 vaccination coverage was lower in rural counties (38.9%) than in urban counties (45.7%) overall and among adults aged 18-64 years (29.1% rural, 37.7% urban), those aged ≥65 years (67.6% rural, 76.1% urban), women (41.7% rural, 48.4% urban), and men (35.3% rural, 41.9% urban). Vaccination coverage varied among jurisdictions: 36 jurisdictions had higher coverage in urban counties, five had higher coverage in rural counties, and five had similar coverage (i.e., within 1%) in urban and rural counties; in four jurisdictions with no rural counties, the urban-rural comparison could not be assessed. A larger proportion of persons in the most rural counties (14.6%) traveled for vaccination to nonadjacent counties (i.e., farther from their county of residence) compared with persons in the most urban counties (10.3%). As availability of COVID-19 vaccines expands, public health practitioners should continue collaborating with health care providers, pharmacies, employers, faith leaders, and other community partners to identify and address barriers to COVID-19 vaccination in rural areas (2).

National, Regional, State, and Selected Local Area Vaccination Coverage Among Adolescents Aged 13-17 Years - United States, 2019.

Three vaccines are recommended by the Advisory Committee on Immunization Practices (ACIP) for routine vaccination of adolescents aged 11-12 years to protect against 1) pertussis; 2) meningococcal disease caused by types A, C, W, and Y; and 3) human papillomavirus (HPV)-associated cancers (1). At age 16 years, a booster dose of quadrivalent meningococcal conjugate vaccine (MenACWY) is recommended. Persons aged 16-23 years can receive serogroup B meningococcal vaccine (MenB), if determined to be appropriate through shared clinical decision-making. CDC analyzed data from the 2019 National Immunization Survey-Teen (NIS-Teen) to estimate vaccination coverage among adolescents aged 13-17 years in the United States.* Coverage with ≥1 dose of HPV vaccine increased from 68.1% in 2018 to 71.5% in 2019, and the percentage of adolescents who were up to date† with the HPV vaccination series (HPV UTD) increased from 51.1% in 2018 to 54.2% in 2019. Both HPV vaccination coverage measures improved among females and males. An increase in adolescent coverage with ≥1 dose of MenACWY (from 86.6% in 2018 to 88.9% in 2019) also was observed. Among adolescents aged 17 years, 53.7% received the booster dose of MenACWY in 2019, not statistically different from 50.8% in 2018; 21.8% received ≥1 dose of MenB, a 4.6 percentage point increase from 17.2% in 2018. Among adolescents living at or above the poverty level,§ those living outside a metropolitan statistical area (MSA)¶ had lower coverage with ≥1 dose of MenACWY and with ≥1 HPV vaccine dose, and a lower percentage were HPV UTD, compared with those living in MSA principal cities. In early 2020, the coronavirus disease 2019 (COVID-19) pandemic changed the way health care providers operate and provide routine and essential services. An examination of Vaccines for Children (VFC) provider ordering data showed that vaccine orders for HPV vaccine; tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap); and MenACWY decreased in mid-March when COVID-19 was declared a national emergency (Supplementary Figure 1, https://stacks.cdc.gov/view/cdc/91795). Ensuring that routine immunization services for adolescents are maintained or reinitiated is essential to continuing progress in protecting persons and communities from vaccine-preventable diseases and outbreaks.

Spatial dynamics and the basic reproduction number of the 1991-1997 Cholera epidemic in Peru.

After being cholera free for over 100 years, Peru experienced an unprecedented epidemic of Vibrio cholerae O1 that began in 1991 and generated multiple waves of disease over several years. We developed a mechanistic transmission model that accounts for seasonal variation in temperature to estimate spatial variability in the basic reproduction number ([Formula: see text]), the initial concentration of vibrios in the environment, and cholera reporting rates. From 1991-1997, cholera spread following a multi-wave pattern, with weekly incidence concentrated during warm seasons. The epidemic first hit the coastal departments of Peru and subsequently spread through the highlands and jungle regions. The correlation between model predictions and observations was high (range in R2: 58% to 97%). Department-level population size and elevation explained significant variation in spatial-temporal transmission patterns. The overall R0 across departments was estimated at 2.1 (95% CI: 0.8,7.3), high enough for sustained transmission. Geographic-region level [Formula: see text] varied substantially from 2.4 (95% CI: 1.1, 7.3) for the coastal region, 1.9 (0.7, 6.4) for the jungle region, and 1.5 (0.9, 2.2) for the highlands region. At the department level, mean [Formula: see text] ranged from 0.8 to 6.9. Department-level [Formula: see text] were correlated with overall observed attack rates (Spearman ρ = 0.59, P = 0.002), elevation (ρ = -0.4, P = 0.04), and longitude (ρ = -0.6, P = 0.004). We find that both [Formula: see text] and the initial concentration of vibrios were higher in coastal departments than other departments. Reporting rates were low, consistent with a substantial fraction of asymptomatic or mild cases associated with the El Tor cholera biotype. Our results suggest that cholera vibrios, autochthonous to plankton in the natural aquatic environment, may have triggered outbreaks in multiple coastal locations along the Pacific coast of Peru. Our methodology could be useful to investigate multi-wave epidemics of cholera and could be extended to conduct near real-time forecasts and investigate the impact of vaccination strategies.