Test-negative Design Study Research Articles

Nirsevimab effectiveness on paediatric emergency visits for RSV bronchiolitis: a test-negative design study.

Our findings advocate for nirsevimab widespread adoption to alleviate the burden of RSV bronchiolitis in paediatric emergency departments. NCT04743609 (date of registration: February 4, 2021). • Each year, RSV-bronchiolitis places significant pressure on pediatric emergency services. • France is one of the first countries in the world to have implemented nirsevimab in septembre 2023. • Nirsevimab effectiveness on pediatric emergency visits for RSV-bronchiolitis has been estimated to 82.5% (95% CI[68.0-90.8]) in our study. • The effectiveness was as strong to prevent hospitalizations and sever illnesses.

P-2073. COVID-19 Vaccine Effectiveness in Patients with Lung Cancer and Mesothelioma in the Omicron Era

Abstract Background Since the Omicron variant emerged, uptake of booster doses of COVID-19 vaccines has gradually decreased both in the general population and among individuals at increased risk of severe COVID-19, such as patients with lung cancer. COVID-19 vaccine effectiveness (VE) has not been estimated in patients with lung cancer in the Omicron era. Methods In this test-negative design study using linked population-based cancer registry, health administrative, vaccination, and public health surveillance databases, we included all patients with active lung cancer or mesothelioma living in Ontario, Canada, who were tested for SARS-CoV-2 by RT-PCR from January 2, 2022, to August 31, 2023. We estimated VE against COVID-19-related severe outcomes (hospitalization or death) 7-179 days and ≥180 days following vaccination. Results During the study period, 13,622 patients with active lung cancer or mesothelioma underwent SARS-CoV-2 testing, with 1,371 (10.1%) positive. After exclusions, we analyzed 6,037 testing episodes, including 1,354 test-positive and 4,683 randomly selected test-negative episodes. Overall, COVID-19-associated hospitalization and mortality rates were 7.3% and 4.0%, respectively. Across both groups, 126/439 hospitalized patients (28.7%) and 116/5,598 non-hospitalized patients died (2.1%) (p=0.001). After multivariable adjustment, VE against severe COVID-19 was 56% (95%CI, 29%, 72%) 7-179 after vaccination and 10% (-45%, 44%) ≥180 days after vaccination. Conclusion Overall, COVID-19 VE against severe outcomes appears to be considerably lower for patients with active lung cancer or mesothelioma than the general population and decreases substantially beyond 180 days after vaccination. Our finding supports administration of COVID-19 booster doses in patients with lung cancer and mesothelioma every 6 months. Disclosures All Authors: No reported disclosures

P-2364. Estimated Additional Burden Averted for the 2022-2023 influenza season from Use of Cell-Based Influenza Vaccines Compared to Egg-Based Influenza Vaccines Among People 0-64 Years of Age in the United States

Abstract Background Estimation of burden averted is useful to contextualize the impact of differentiated vaccines. Traditional influenza vaccine production in eggs can introduce egg-adaptive mutations. Cell-based influenza vaccines avoid egg-adaptation, potentially improving match to circulating influenza viruses and thereby vaccine effectiveness (VE). This study modeled the public health impact if all people aged 0-64 years vaccinated in the United States during the 2022-2023 influenza season had received either cell-based inactivated quadrivalent influenza vaccine (ccIIV4) or egg-based inactivated quadrivalent influenza vaccine (IIV4).Table 1:Number of outcomes prevented from use of IIV4 and ccIIV4, individuals 0—64 Years Methods The modeling method used by the US Centers for Disease Control and Prevention (CDC) to estimate overall burden averted due to influenza vaccination was extended to a relative VE (rVE) context. The model utilized 2022-2023 CDC data on influenza vaccine uptake, influenza incidence, influenza-related healthcare resource (HRU) use and deaths. CDC estimates of absolute VE (aVE) (any vaccine) were used as the aVE of IIV4. We applied an rVE of 7.7% (0.9 to 13.9%), estimated in a 2022-2023 retrospective test-negative design study. Base-case results were validated with deterministic (DSA) and probabilistic (PSA) sensitivity analyses.Table 2:Number of additional outcomes prevented from use of ccIIV4 compared to IIV4, by age group Results Table 1 shows the anticipated number of symptomatic influenza cases and associated HRU and deaths that would have been averted if all vaccinated people 0-64 years of age received either ccIIV4 or IIV4 and Table 2 shows the additional burden averted by age. Use of ccIIV4 would result in prevention of an additional 622,826 symptomatic illnesses, 307,682 outpatient visits, 3,680 hospitalizations, 559 intensive care unit (ICU) admissions, and 127 deaths compared to IIV4. DSA results showed that the rVE estimate was associated with the most variability, followed by influenza-related HRU and deaths. Mean PSA results were all within a 0.1% difference of base-case results. Conclusion Use of ccIIV4 instead of IIV4 during the 2022-2023 influenza seasons in the US would have had a substantial public health impact on the population 0-64 years of age due to prevention of an additional 622,826 symptomatic illnesses as well as proportionate reductions in associated HRU and deaths. Disclosures Ian McGovern, MPH, CSL Seqirus: Employee|CSL Seqirus: Stocks/Bonds (Public Company) Alicia N. Stein, MBiostats, PhD, CSL Seqirus: Employee|CSL Seqirus: Stocks/Bonds (Public Company) Mendel Haag, PhD, PharmD, CSL Seqirus: Employment|CSL Seqirus: Stocks/Bonds (Public Company)

Effectiveness of rotavirus vaccine following introduction in the childhood immunization program in Northeast India.

Rotavirus diarrhoea is a major cause of mortality and morbidity in children under five years of age. The WHO has recommended vaccination against this agent especially in countries with high mortality rates. As India accounts for almost a quarter of worldwide rotaviral diarrhoea cases, the government has introduced indigenously manufactured vaccines in the national immunization schedule which has been implemented in four phases. This study was conducted to assess the effectiveness of the vaccine used in the national immunization program in the state of Manipur in North-east India. A test negative study design was used comparing rotavirus positive diarrhoeal children to rotavirus negative diarrhoeal children. All children ≤ 5 years presenting with acute diarrhoea were enrolled in the study and antigen detection enzyme-immuno assay was done to detect presence of rotavirus. All rotavirus positive patients were taken as cases and compared with rotavirus negative controls. 63 rotavirus positive cases and 121 rotavirus negative controls were enrolled in the study. Vaccination rate among cases was significantly lower than controls (31.7% vs 68.6%, p < .001). Vaccine effectiveness of completed vaccination series was found to be 94% against rotaviral infection and 98.1% against severe disease and need for hospitalization. Current rotaviral vaccine used in the national immunization schedule of India is effective in preventing rotaviral diarrhoea in the state of Manipur. Sustained vaccination will reduce the mortality and morbidity of rotaviral diarrhoea in this region.

Update to: Study Pre-protocol for “BronchStart - The Impact of the COVID-19 Pandemic on the Timing, Age and Severity of Respiratory Syncytial Virus (RSV) Emergency Presentations; a Multi-Centre Prospective Observational Cohort Study”

Background In 2021 we launched the BronchStart study, which collected information on 17,899 presentations in children with serious respiratory tract infections following the release of lockdown restrictions. Our study informed the Joint Committee on Vaccination and Immunisation’s decision to recommend the introduction maternal respiratory syncytial virus (RSV) vaccination, which was introduced in the United Kingdom in August/September 2024. Study question We modified our original protocol to conduct a United Kingdom-wide assessment of maternal vaccination against RSV. Methods and likely impact We will conduct a multi-centre study, utilising the PERUKI network used in the original BronchStart study, to assess the effectiveness of maternal vaccination using a test-negative study design. We will gather detailed clinical information on children admitted with bronchiolitis in the post-RSV vaccination era, and understand possible reasons for incomplete vaccine uptake.

Bias in control selection associated with the use of rapid tests in influenza vaccine effectiveness studies.

In test-negative design studies that use rapid tests to estimate influenza vaccine effectiveness (VE) a common concern is case/control misclassification due to imperfect test sensitivity and specificity. However, an imperfect test can also fail to exclude from the control group people that do not represent the source population, including people infected with other influenza types or other vaccine-preventable respiratory viruses for which vaccination status is correlated. We investigated these biases by comparing the effectiveness of seasonal 2023/24 influenza vaccination against influenza A and B based on PCR versus rapid test results, excluding controls who tested positive for SARS-CoV-2 or the other type of influenza. By PCR, VE against influenza A was 49% (95%CI 26-65%) after exclusion of PCR-confirmed influenza B and SARS-CoV-2 controls. Corresponding VE against influenza B was 65% (95%CI 35-81%). VE estimated by adjusting for COVID-19 vaccination status yielded similar estimates to the scenario that excluded SARS-CoV-2-positive controls. When case/control status and exclusions from test-negative controls were determined by rapid test, VE was reduced by 5-15 percentage points. Bias correction methods were able to reduce these discrepancies. When estimating VE from a test-negative study using rapid test results, methods to correct misclassification bias are recommended.

COVID-19 vaccine effectiveness and hybrid immunity in the respiratory season of 2022-23 in Hungary

Abstract Background There has been an increase in COVID-19 vaccine hesitancy among the general population, accompanied by a decline in confidence that vaccines provide adequate protection. We estimated the effectiveness of the COVID-19 vaccines (CVE) and hybrid immunity against medically attended COVID-19 during the 2022-2023 respiratory season in Hungary. Methods We conducted a test-negative design study involving 68 GPs. Patients aged ≥18 years presenting with acute respiratory infection were swabbed. Cases and controls were patients testing positive and negative for SARS-CoV-2 by RT-PCR, respectively. Exposure was defined as having received at least one COVID-19 booster dose, taking into account the time since the last vaccination. CVE was estimated using logistic regression, adjusted for symptom onset date, age, chronic condition and sex. Results We included 247 cases and 1073 controls in the analysis. 196 samples were sequenced, and Omicron BA.5, BQ.1 and XBB.1 were the most frequent sub-variants. The CVE was 52.9% (95% CI: 15.2-73.9%), and 72.3% (95% CI: 32.0-88.7%) in the 18-59, and 60+-year-old population who received the final dose within the past year, respectively. Self-reported COVID-19 in the previous 60-365 days did not confer protection against reinfection, however, when combined with booster vaccination, it reduced the risk of COVID-19 by 63.0% (95% CI: −28.0-89.3%) and 87.6% (95% CI: 26.4-97.9%) among the 18-59 and 60+ age groups, respectively. Conclusions Booster vaccination within one year after the last dose confers significant protection against symptomatic infection, particularly among the elderly. Those who have previously been infected with SARS-CoV-2 may also benefit from booster vaccinations. Key messages • COVID-19 booster campaigns must be intensified, focusing mainly on the elderly. • Providing clear guidance on the timing and target groups of vaccination and emphasising the benefits of vaccination can help to achieve higher coverage.

Update to: Study Pre-protocol for "BronchStart - The Impact of the COVID-19 Pandemic on the Timing, Age and Severity of Respiratory Syncytial Virus (RSV) Emergency Presentations; a Multi-Centre Prospective Observational Cohort Study".

In 2021 we launched the BronchStart study, which collected information on 17,899 presentations in children with serious respiratory tract infections following the release of lockdown restrictions. Our study informed the Joint Committee on Vaccination and Immunisation's decision to recommend the introduction maternal respiratory syncytial virus (RSV) vaccination, which was introduced in the United Kingdom in August/September 2024. We modified our original protocol to conduct a United Kingdom-wide assessment of maternal vaccination against RSV. We will conduct a multi-centre study, utilising the PERUKI network used in the original BronchStart study, to assess the effectiveness of maternal vaccination using a test-negative study design. We will gather detailed clinical information on children admitted with bronchiolitis in the post-RSV vaccination era, and understand possible reasons for incomplete vaccine uptake.

Potential Biases in Test-Negative Design Studies of COVID-19 Vaccine Effectiveness Arising from the Inclusion of Asymptomatic Individuals.

The test-negative design (TND) is a popular method for evaluating vaccine effectiveness (VE). A "classical" TND study includes symptomatic individuals tested for the disease targeted by the vaccine to estimate VE against symptomatic infection. However, recent applications of the TND have attempted to estimate VE against infection by including all tested individuals, regardless of their symptoms. In this article, we use directed acyclic graphs and simulations to investigate potential biases in TND studies of COVID-19 VE arising from the use of this "alternative" approach, particularly when applied during periods of widespread testing. We show that the inclusion of asymptomatic individuals can potentially lead to collider stratification bias, uncontrolled confounding by health and healthcare-seeking behaviors (HSBs), and differential outcome misclassification. While our focus is on the COVID-19 setting, the issues discussed here may also be relevant in the context of other infectious diseases. This may be particularly true in scenarios where there is either a high baseline prevalence of infection, a strong correlation between HSBs and vaccination, different testing practices for vaccinated and unvaccinated individuals, or settings where both the vaccine under study attenuates symptoms of infection and diagnostic accuracy is modified by the presence of symptoms.

Real-world effectiveness of original BNT162b2 mRNA COVID-19 against symptomatic Omicron infection among children 5–11 years of age in Brazil: A prospective test-negative design study

ObjectiveTo estimate original wild-type BNT162b2 effectiveness against symptomatic Omicron infection among children 5–11 years of age. MethodsThis prospective test-negative, case-control study was conducted in Toledo, southern Brazil, from June 2022 to July 2023. Patients were included if they were aged 5–11 years, sought care for acute respiratory symptoms in the public health system, and were tested for SARS-CoV-2 using reverse transcription polymerase chain reaction. In the primary analysis, we determined the effectiveness of two doses of original wild-type BNT162b2 against symptomatic COVID-19. The reference exposure group was the unvaccinated. ResultsA total of 757 children were enrolled; of these, 461 (25 cases; 436 controls) were included in the primary analysis. Mean age was 7.4 years, 49.7 % were female, 34.6 % were obese, and 14.1 % had chronic pulmonary disease. Omicron accounted for 100 % of all identified SARS-CoV-2 variants with BA.5, BQ.1, and XBB.1 accounting for 35.7 %, 21.4 % and 21.4 %, respectively. The adjusted estimate of two-dose vaccine effectiveness against symptomatic Omicron was 3.1 % (95 % CI, -133.7 % to 61.8 %) after a median time between the second dose and the beginning of COVID-19 symptoms of 192.5 days (interquartile range, 99 to 242 days). ConclusionIn this study with children 5–11 years of age, a two dose-schedule of original wild-type BNT162b2 was not associated with a significant protection against symptomatic Omicron infection after a median time between the second dose and the beginning of COVID-19 symptoms of 192 days, although the study may have been underpowered to detect a clinically important difference. Trial registration numberClinicalTrials.gov number, NCT05403307 (https://classic.clinicaltrials.gov/ct2/show/NCT05403307)

Effectiveness of influenza vaccine among the population in Chongqing, China, 2018–2022: A test negative design-based evaluation

ABSTRACT Influenza vaccination is the most cost-effective strategy for influenza prevention. Influenza vaccines have been found to be effective against symptomatic and medically attended outpatient influenza illnesses. However, there is currently a lack of data regarding the effectiveness of inactivated influenza vaccines in Chongqing, China. We conducted a prospective observational test-negative design study. Outpatient and emergency cases presenting with influenza-like illnesses (ILI) and available influenza reverse transcription polymerase chain reaction (RT-PCR) were selected and classified as cases (positive influenza RT-PCR) or controls (negative influenza RT-PCR). A total of 7,307 cases of influenza and 7,905 control subjects were included in this study. The overall adjusted influenza vaccine effectiveness (IVE) was 44.4% (95% confidence interval (CI): 32.5–54.2%). In the age groups of less than 6 years old, 6–18 years old, and 19–59 years old, the adjusted IVE were 32.2% (95% CI: 10.0–48.9%), 48.2% (95% CI: 30.6–61.4%), and 72.0% (95% CI: 43.6–86.1%). The adjusted IVE for H1N1, H3N2 and B (Victoria) were 71.1% (95% CI: 55.4–81.3%), 36.1% (95% CI: 14.6–52.2%) and 33.7% (95% CI: 14.6–48.5%). Influenza vaccination was effective in Chongqing from 2018 to 2022. Evaluating IVE in this area is feasible and should be conducted annually in the future.

Hypothesis testing and sample size considerations for the test-negative design

The test-negative design (TND) is an observational study design to evaluate vaccine effectiveness (VE) that enrolls individuals receiving diagnostic testing for a target disease as part of routine care. VE is estimated as one minus the adjusted odds ratio of testing positive versus negative comparing vaccinated and unvaccinated patients. Although the TND is related to case–control studies, it is distinct in that the ratio of test-positive cases to test-negative controls is not typically pre-specified. For both types of studies, sparse cells are common when vaccines are highly effective. We consider the implications of these features on power for the TND. We use simulation studies to explore three hypothesis-testing procedures and associated sample size calculations for case–control and TND studies. These tests, all based on a simple logistic regression model, are a standard Wald test, a continuity-corrected Wald test, and a score test. The Wald test performs poorly in both case–control and TND when VE is high because the number of vaccinated test-positive cases can be low or zero. Continuity corrections help to stabilize the variance but induce bias. We observe superior performance with the score test as the variance is pooled under the null hypothesis of no group differences. We recommend using a score-based approach to design and analyze both case–control and TND. We propose a modification to the TND score sample size to account for additional variability in the ratio of controls over cases. This work enhances our understanding of the data generating mechanism in a test-negative design (TND) and how it is distinct from that of a case-control study due to its passive recruitment of controls.

Relative vaccine effectiveness of MF59-adjuvanted vs high-dose trivalent inactivated influenza vaccines for prevention of test-confirmed influenza hospitalizations during the 2017–2020 influenza seasons

ObjectivesThis study evaluated relative vaccine effectiveness (rVE) of MF59-adjuvanted trivalent inactivated influenza vaccine (aTIV) vs high-dose trivalent inactivated influenza vaccine (HD-TIV) for prevention of test-confirmed influenza emergency department visits and/or inpatient admissions (“ED/IP”) and for IP admissions alone pooled across the 2017–2020 influenza seasons. Exploratory individual season analyses were also performed. MethodsThis retrospective test-negative design study included United States (US) adults age ≥65 years vaccinated with aTIV or HD-TIV who presented to an ED or IP setting with acute respiratory or febrile illness during the 2017–2020 influenza seasons. Test-positive cases and test-negative controls were grouped by vaccine received. The rVE of aTIV vs HD-TIV was evaluated using a combination of inverse probability of treatment weighting and logistic regression to adjust for potential confounders. ResultsPooled analyses over the three seasons found no significant differences in the rVE of aTIV vs HD-TIV for prevention of test-confirmed influenza ED/IP (−2.5% [−19.6, 12.2]) visits and admissions or IP admissions alone (−1.6% [−22.5, 15.7]). The exploratory individual season analyses also showed no significant differences. ConclusionsEvidence from the 2017–2020 influenza seasons indicates aTIV and HD-TIV are comparable for prevention of test-confirmed influenza ED/IP visits in US adults age ≥65 years.

Effectiveness of COVID-19 vaccines administered in the 2023 autumnal campaigns in Europe: Results from the VEBIS primary care test-negative design study, September 2023–January 2024

In autumn 2023, European vaccination campaigns predominantly administered XBB.1.5 vaccine. In a European multicentre study, we estimated 2023 COVID-19 vaccine effectiveness (VE) against laboratory-confirmed symptomatic infection at primary care level between September 2023 and January 2024. Using a test-negative case–control design, we estimated VE in the target group for COVID-19 vaccination overall and by time since vaccination. We included 1057 cases and 4397 controls. Vaccine effectiveness was 40 % (95 % CI: 26–53 %) overall, 48 % (95 % CI: 31–61 %) among those vaccinated < 6 weeks of onset and 29 % (95 % CI: 3–49 %) at 6–14 weeks. Our results suggest that COVID-19 vaccines administered to target groups during the autumn 2023 campaigns showed clinically significant effectiveness against laboratory-confirmed, medically attended symptomatic SARS-CoV-2 infection in the 3 months following vaccination. A longer study period will allow for further variant-specific COVID-19 VE estimates, better understanding decline in VE and informing booster administration policies.

Pneumococcal vaccination effectiveness (PCV13 and PPSV23) in individuals with and without reduced kidney function: a test-negative design study.

Streptococcus pneumoniae vaccination effectiveness (VE) in individuals with reduced kidney function is unknown. We estimated pneumococcal conjugate vaccine (PCV13), pneumococcal polysaccharide vaccine (PPSV23), and combined PCV13 and PPSV23 effectiveness against pneumococcal disease in individuals with and without reduced estimated glomerular filtration rate (eGFR). All eligible individuals (case and controls) were adults (aged ≥18 years) hospitalized within the Geisinger Health System and required to have S. pneumoniae urinary antigen testing (i.e. test-negative design). Vaccination records were obtained from the electronic health record and statewide vaccination registry. After controlling for the probability of receiving a pneumococcal vaccine, we used multivariable logistic regression models to estimate the odds ratios (ORs) of vaccination between those who did and did not meet the S. pneumoniae case definition. VE was calculated as (1-OR)×100%. There were 180 cases and 3889 controls (mean age 69 years, female 48%, white 97%, mean eGFR 71mL/min/1.73m2). The adjusted population PCV13 VE was 39% (95% CI 13%-58%), and combination PCV13 and PPSV23 was 39% (95% CI 12%-58%). PPSV23 VE was -3.7% (95% CI -57% to 32%). Stratified by eGFR, adjusted PCV13 VE was consistent in eGFR ≥60 [VE 38% (95% CI 2.9%-61%)] and 30-59 [VE 61% (95% CI 24%-80%)] without significant interaction. VE was not calculable for eGFR <30 due to small sample size. PCV13 vaccination was associated with reduced risk of S. pneumoniae hospitalization in individuals with a reduced eGFR (30-59mL/min/1.73m2).

Effectiveness and safety of COVID-19 vaccines on maternal and perinatal outcomes: a systematic review and meta-analysis

ObjectiveTo assess the effects of COVID-19 vaccines in women before or during pregnancy on SARS-CoV-2 infection-related, pregnancy, offspring and reactogenicity outcomes.DesignSystematic review and meta-analysis.Data sourcesMajor databases between December 2019 and...

Effectiveness of Covid-19 Vaccines Administered in the 2023 Autumnal Campaigns in Europe: Results from the Vebis Primary Care Test-Negative Design Study, September 2023–January 2024

Effectiveness of Covid-19 Vaccines Administered in the 2023 Autumnal Campaigns in Europe: Results from the Vebis Primary Care Test-Negative Design Study, September 2023–January 2024

Estimating protection afforded by prior infection in preventing reinfection: applying the test-negative study design.

The COVID-19 pandemic has highlighted the need to use infection testing databases to rapidly estimate effectiveness of prior infection in preventing reinfection ($P{E}_S$) by novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. Mathematical modeling was used to demonstrate a theoretical foundation for applicability of the test-negative, case-control study design to derive $P{E}_S$. Apart from the very early phase of an epidemic, the difference between the test-negative estimate for $P{E}_S$ and true value of $P{E}_S$ was minimal and became negligible as the epidemic progressed. The test-negative design provided robust estimation of $P{E}_S$ and its waning. Assuming that only 25% of prior infections are documented, misclassification of prior infection status underestimated $P{E}_S$, but the underestimate was considerable only when > 50% of the population was ever infected. Misclassification of latent infection, misclassification of current active infection, and scale-up of vaccination all resulted in negligible bias in estimated $P{E}_S$. The test-negative design was applied to national-level testing data in Qatar to estimate $P{E}_S$ for SARS-CoV-2. $P{E}_S$ against SARS-CoV-2 Alpha and Beta variants was estimated at 97.0% (95% CI, 93.6-98.6) and 85.5% (95% CI, 82.4-88.1), respectively. These estimates were validated using a cohort study design. The test-negative design offers a feasible, robust method to estimate protection from prior infection in preventing reinfection.

Maternal mRNA COVID-19 Vaccination During Pregnancy and Delta or Omicron Infection or Hospital Admission in Infants: Test Negative Design Study

(BMJ. 2023;380:e074035) Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) rates are higher in infants than in older children. Passive immunity has been shown to help prevent other infections, such as pertussis, in infants through the transfer of maternal antibodies following vaccination during pregnancy. SARS-CoV-2 antibodies are found to be present in breastmilk, umbilical cord blood, and infant serum specimens following maternal vaccination during pregnancy and infection, and emerging research suggests maternal COVID-19 vaccination reduces infant infection and hospital admission rates. This study aimed to determine whether maternal vaccination during pregnancy with 2 primary doses or 2 primary doses plus booster of the mRNA COVID-19 vaccine series reduces the infection of omicron and delta SARS-CoV-2 and hospital admission of infants within 6 months following delivery.

Effectiveness of COVID-19 vaccines in Ecuador: A test-negative design

BackgroundThe COVID-19 pandemic poses a significant global health threat, characterized by high morbidity, severity, and the emergence of concerning variants. Latin America has been greatly affected, with high infection and mortality rates. Vaccination plays a crucial role in mitigating severe disease and controlling the pandemic. This study aims to assess the effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 severe acute respiratory infections (SARI) in hospitalized vaccination target groups in Ecuador. MethodsThis is a test-negative design study. We used data reported through sentinel surveillance of SARI between May 2021 and March 2022 in Ecuador. Patients with case criteria of SARI and hospitalized for a minimum of 24 hours were included in the study. Cases were defined as patients with SARI with a positive RT-qPCR test for SARS-CoV-2 and controls were those with a negative result. Information on vaccination status was obtained from the national vaccination registry, a valid dose of vaccination was considered when it was administered at least 14 days prior to symptom onset. Vaccine effectiveness (VE) (1-OR/OR) was calculated using a logistic regression. ResultsA total of 1,277 patients were included in the analysis of VE. The adjusted vaccine effectiveness (aVE) in preventing hospitalization, adjusted for sex, age group, presence of one or more comorbidities, and period of the predominance of the omicron variant, was 44.5% for the partial primary schedule, 74.7% for the complete primary schedule, and 79.9% for the complete primary schedule plus booster doses. The aVE in avoiding ICU admissions was close to 80% with both the complete primary schedule and the booster doses, and in avoiding deaths, the aVE was 89% and 98%, respectively. ConclusionsIn Ecuador, COVID-19 vaccination prevents hospitalizations, ICU admissions, and deaths. The effectiveness of the vaccines improves with more doses, offering increased protection across all age groups.