Vaccinated COVID-19 Index Cases Are Less Likely to Transmit SARS-CoV-2 to Their Household Contacts: A Cohort Study.

The aim of this study was to evaluate the impact of index case vaccination on SARS-CoV-2 transmission to household contacts. In our epidemiological cohort study (May 2022-November 2023), we surveyed registered index case vaccination status and test results for contacts (testing on day 0, and on day 7 for negative contacts) and calculated the secondary attack rate (SAR), i.e., newly infected contacts/susceptible included contacts. The association of the independent variable, index case COVID-19 vaccination (yes/no), with household contact infection was determined using the adjusted odds ratio (aOR) and its 95% confidence interval (CI). We recorded 181 index cases and 314 contacts, of whom 250 agreed to participate; 16 contacts were excluded upon testing positive on day 0. Of the 234 included contacts, 49.1% were women, and the mean (SD) age was 51.9 (19.8) years. The overall SAR of 37.2% (87/234) was lower in the contacts of both vaccinated index cases (34.9% vs. 63.2%; p = 0.014) and index cases with a previous SARS-CoV-2 infection history (27.0% vs. 46.3%; p = 0.002). Index case vaccination showed a protective effect against infection for their household contacts (aOR = 0.21; 95% CI: 0.07, 0.67). The household SAR was high when the Omicron variant circulated. Vaccinated index cases were less likely to transmit SARS-CoV-2 to their contacts.

Factors Associated with Non-Adherence to Tuberculosis Preventive Treatment among Adult Contacts of Pulmonary Tuberculosis Cases with Latent Tuberculosis Infection in Catalonia, Spain, in 2019-2021.

The aim of this study was to identify factors associated with non-adherence to tuberculosis (TB) preventive treatment among contacts with latent TB infection for new cases of pulmonary TB cases reported in Catalonia in 2019-2021. All contacts aged 18 years or older with a latent TB infection who received a TB preventive treatment were included in the study. The Chi square test and the odds ratios (OR) were used to assess the association between non-adherence to TB preventive treatment and the study variables; a p < 0.05 was considered statistically significant. Multiple logistic regression analysis was used to detect the independent factors associated with TB preventive treatment non-adherence; a p < 0.05 was considered statistically significant. The percentage of non-adherence to TB preventive treatment found in this study was 23.7%. A multivariable logistic regression analysis determined that the following factors were significantly associated with TB preventive treatment non-adherence among adult contacts: "exposure at school or workplace" (aOR = 3.34), "exposure to an index case without laboratory confirmation of TB" (aOR = 2.07), "immigrant contact" (aOR = 1.81), "male gender" (aOR = 1.75) and "exposure duration < 6 h per week or sporadic" (aOR = 1.60. By contrast, the factor "short-term TB preventive treatment regimen" (aOR = 0.38) was significantly associated with a lower treatment non-adherence. Adherence to TB preventive treatment should be improved among adult contacts of TB pulmonary cases with latent TB infection by recommending short-term treatment regimens and by developing health education activities, with a greater focus on contacts with factors associated with treatment non-adherence.

Effectiveness of Adapted COVID-19 Vaccines and Ability to Establish Herd Immunity against Omicron BA.1 and BA4-5 Variants of SARS-CoV-2.

The emergence of novel SARS-CoV-2 variants has raised concerns about the ability of COVID-19 vaccination programs to establish adequate herd immunity levels in the population. This study assessed the effectiveness of adapted vaccines in preventing SARS-CoV-2 infection and the ability of the adapted vaccines to establish herd immunity against emerging Omicron variants. A systematic literature review was conducted to estimate the absolute vaccine effectiveness (aVE) in preventing SARS-CoV-2 infection using adapted vaccines targeting Omicron variants. The ability of the adapted vaccines to establish herd immunity was assessed by taking into account the following factors: aVE, Ro values of SARS-CoV-2 and the use of non-pharmacological interventions (NPIs). This study found meta-analysis-based aVEs in preventing severe disease and SARS-CoV-2 infection of 56-60% and 36-39%, respectively. Adapted vaccines could not establish herd immunity against the Omicron BA.1 and BA.4-5 variants without using non-pharmacological interventions (NPIs). The adapted vaccines could establish herd immunity only by achieving >80% vaccination coverage, using NPIs with greater effectiveness and when 20-30% of individuals were already protected against SARS-CoV-2 in the population. New adapted COVID-19 vaccines with greater effectiveness in preventing SARS-CoV-2 infection must be developed to increase herd immunity levels against emerging SARS-CoV-2 variants in the population.

Strategies to Increase the Percentages of Vaccination Coverage.

In 2012, the WHO proposed the Global Vaccine Action Plan (GVAP) 2011-2020 to promote essential or routine vaccines among all children of the world [...].

High Influenza Vaccine Effectiveness and Absence of Increased Influenza-like-Illness Epidemic Activity in the 2021-2022 Influenza Season in Catalonia (Spain) Based on Surveillance Data Collected by Sentinel Pharmacies.

Influenza surveillance and influenza vaccination are the key activities for preventing and controlling influenza epidemics. The study assessed the influenza surveillance and influenza vaccination data obtained from sentinel pharmacies of Catalonia, Spain, in the 2021-2022 influenza season. The sentinel pharmacies were selected from all community pharmacies to report all influenza-like illness (ILI) cases detected during the 2021-2022 influenza season and collect influenza surveillance and influenza vaccination data. The ILI cases were identified based on European Centre for Disease Control (ECDC) criteria. The moving epidemic method (MEM) was used to assess the ILI epidemic activity. The screening method was used to assess influenza vaccination effectiveness in patients aged 65-or-more years old. The sentinel pharmacies reported 212 ILI cases with a negative COVID-19 test and a total number of 412 ILI cases. An absence of increased ILI epidemic activity was observed in the 2021-2022 influenza season based on two criteria: (1) Number of ILI cases reported per week in the 2021-2022 influenza season significantly lower than the MEM-based epidemic threshold. (2) Mean number of ILI cases reported per week in the 2021-2022 influenza season significantly lower than during the ILI/influenza epidemic periods detected from 2017 to 2020 using the same methodology. Influenza vaccination was effective in preventing ILI among patients aged 65-or-more-years old. The absence of the influenza epidemic during the 2021-2022 influenza season could be explained by influenza vaccination and COVID-19 prevention measures (wearing face masks, social distancing). The sentinel pharmacies provided influenza surveillance data not provided by traditional influenza surveillance systems.

Percentages of Vaccination Coverage Required to Establish Herd Immunity against SARS-CoV-2.

The pandemic associated with SARS-CoV-2 is a worldwide public health challenge. The WHO has proposed to achieve 70% COVID-19 vaccination coverage in all countries by mid-2022. Nevertheless, the prevention strategy based on COVID-19 vaccination and other applied prevention measures has not been sufficient to prevent SARS-CoV-2 epidemic waves. This study assessed the vaccination coverage that would be required to establish herd immunity against SARS-CoV-2, taking into account virus transmissibility (Ro values from 1.1 to 10) and COVID-19 vaccination effectiveness. The study found that high percentages of vaccination coverage and high levels of vaccination effectiveness are necessary to block the transmission of Omicron and other SARS-CoV-2 variants with greater infectious capacity. COVID-19 vaccination programs could establish herd immunity against SARS-CoV-2, with Ro values ranging from 3 to 10 and levels of COVID-19 vaccination effectiveness of 70-100%. Factors reducing COVID-19 vaccination effectiveness (emergent variants, infections among vaccinated individuals, high risk individuals) and factors increasing SARS-CoV-2 transmissibility (close settings) increased the percentages of vaccination coverage that would be required to establish herd immunity. Two measures should be implemented to establish herd immunity against SARS-CoV-2: (1) achieve ≥ 90% COVID-19 vaccination coverage in all countries worldwide, and (2) increase the effectiveness of COVID-19 vaccines in preventing Omicron infection to at least 88%.

Relative Effectiveness of Cell-Cultured versus Egg-Based Seasonal Influenza Vaccines in Preventing Influenza-Related Outcomes in Subjects 18 Years Old or Older: A Systematic Review and Meta-Analysis.

Avian mutations in vaccine strains obtained from embryonated eggs could impair vaccine effectiveness. We performed a systematic review and meta-analysis of the adjusted relative vaccine effectiveness (arVE) of seed cell-cultured influenza vaccines (ccIV) compared to egg-based influenza vaccines (eIV) in preventing laboratory-confirmed influenza related outcomes (IRO) or IRO by clinical codes, in subjects 18 and over. We completed the literature search in January 2021; applied exclusion criteria, evaluated risk of bias of the evidence, and performed heterogeneity, publication bias, qualitative, quantitative and sensitivity analyses. All estimates were computed using a random approach. International Prospective Register of Systematic Reviews, CRD42021228290. We identified 12 publications that reported 26 adjusted arVE results. Five publications reported 13 laboratory confirmed arVE and seven reported 13 code-ascertained arVE. Nine publications with 22 results were at low risk of bias. Heterogeneity was explained by season. We found a significant 11% (8 to 14%) adjusted arVE favoring ccIV in preventing any IRO in the 2017-2018 influenza season. The arVE was 3% (-2% to 7%) in the 2018-2019 influenza season. We found moderate evidence of a significant advantage of the ccIV in preventing IRO, compared to eIV, in a well-matched A(H3N2) predominant season.

Vaccination Coverage for Routine Vaccines and Herd Immunity Levels against Measles and Pertussis in the World in 2019.

In 2012, the World Health Organization (WHO) established the Global Vaccine Action Plan with the objective to promote essential vaccinations in all countries and achieve at least 90% vaccination coverage for all routine vaccines by 2020. The study assessed the mean percentages of vaccination coverage in 2019 for 13 routine vaccines, vaccination coverage variation from 2015 to 2019, and herd immunity levels against measles and pertussis in 2019 in countries and regions of WHO. In 2019, the mean percentages of vaccination coverage were lower than 90% for 10 (78.9%) routine vaccines. The mean percentages of vaccination coverage also decreased from 2015 to 2019 for six (46.2%) routine vaccines. The prevalence of individuals with vaccine-induced measles immunity in the target measles vaccination population was 88.1%, and the prevalence of individuals with vaccine-induced pertussis immunity in the target pertussis vaccination population was 81.1%. Herd immunity against measles viruses with Ro = 18 was established in 63 (32.5%) countries but not established in any region. Herd immunity against pertussis agents was not established in any country and in any region of WHO. National immunization programs must be improved to achieve ≥90% vaccination coverage in all countries and regions. Likewise, it is necessary to achieve ≥95% vaccination coverage with two doses of measles vaccines and three doses of pertussis vaccines in all countries and regions.

Azithromycin to Prevent Pertussis in Household Contacts, Catalonia and Navarre, Spain, 2012-2013.

We retrospectively assessed the effectiveness of azithromycin in preventing transmission of pertussis to a patient's household contacts. We also considered the duration between symptom onset in the primary patient and azithromycin administration. We categorized contacts into 4 groups: those treated within <7 days, 8-14 days, 15-21 days, and >21 days after illness onset in the primary patient. We studied 476 primary index patients and their 1,975 household contacts, of whom 4.5% were later identified as having pertussis. When contacts started chemoprophylaxis within <21 days after the primary patient's symptom onset, the treatment was 43.9% effective. Chemoprophylaxis started >14 days after primary patient's symptom onset was less effective. We recommend that contacts of persons with pertussis begin chemoprophylaxis within <14 days after primary patient's symptom onset.

Are the Objectives Proposed by the WHO for Routine Measles Vaccination Coverage and Population Measles Immunity Sufficient to Achieve Measles Elimination from Europe?

Background: The World Health Organization (WHO) proposed two-dose measles vaccination coverage of at least 95% of the population and percentages of measles immunity in the population of 85%-95% in order to achieve measles elimination in Europe. The objectives of this study were: (1) to determine the measles vaccination coverage required to establish herd immunity against measles viruses with basic reproduction numbers (Ro) ranging from 6 to 60, and (2) to assess whether the objectives proposed by the WHO are sufficient to establish herd immunity against measles viruses. Methods: The herd immunity effects of the recommended objectives were assessed by considering the prevalence of protected individuals required to establish herd immunity against measles viruses with Ro values ranging from 6 to 60. Results: The study found that percentages of two-dose measles vaccination coverage from 88% to 100% could establish herd immunity against measles viruses with Ro from 6 to 19, assuming 95% measles vaccination effectiveness. The study found that the objective of 95% for two-dose measles vaccination coverage proposed by the WHO would not be sufficient to establish herd immunity against measles viruses with Ro ≥ 10, assuming 95% measles vaccination effectiveness. By contrast, a 97% measles vaccination coverage objective was sufficient to establish herd immunity against measles viruses, with Ro values from 6 to 13. Measles immunity levels recommended in individuals aged 1-4 years (≥85%) and 5-9 years (≥90%) might not be sufficient to establish herd immunity against most measles viruses, while those recommended in individuals aged 10 or more years (≥95%) could be sufficient to establish herd immunity against measles viruses with Ro values from 6 to 20. Conclusion: To meet the goal of measles elimination in Europe, it is necessary to achieve percentages of two-dose measles vaccination coverage of at least 97%, and measles immunity levels in children aged 1-9 years of at least 95%.

Low percentages of measles vaccination coverage with two doses of vaccine and low herd immunity levels explain measles incidence and persistence of measles in the European Union in 2017-2018.

Several factors may explain why measles persisted in the European Union in 2017-2018. The study assessed mean measles vaccination coverage and anti-measles herd immunity levels in the target measles vaccination population in countries of the European Union during the 2015-2017 period. The study found that the measles vaccination coverage with two doses of vaccine was < 95% in 28 (96.5%) countries, and that the prevalence of individuals with vaccine-induced measles protection in the target vaccination population was lower than the herd immunity threshold of 94.4% in 22 (75.9%) countries during 2015-2017. The study found a significant negative correlation between the incidence of measles in 2017-2018 in different countries of the European Union and measles vaccination coverage with two doses of measles vaccine, prevalence of individuals with vaccine-induced measles protection and herd immunity levels in the target measles vaccination population during 2015-2017. Measles vaccination coverage and herd immunity levels did not improve from 2010-2015 to 2015-2017 in the European Union. Low percentages of measles vaccination coverage with two doses of vaccine and low herd immunity levels could explain measles incidence in countries of the European Union in 2017-2018. New measles prevention strategies should be developed to increase measles vaccination coverage and herd immunity levels in the European Union.

Reduction of Direct Health Costs Associated with Pertussis Vaccination with Acellular Vaccines in Children Aged 0-9 Years with Pertussis in Catalonia (Spain).

OBJECTIVES: The aim of this study was to assess direct health costs in children with pertussis aged 0-9 years who were vaccinated, partially vaccinated, and unvaccinated during childhood, and to assess the association between pertussis costs and pertussis vaccination in Catalonia (Spain) in 2012-2013. METHODS: Direct healthcare costs included pertussis treatment, pertussis detection, and preventive chemotherapy of contacts. Pertussis patients were considered vaccinated when they had received 4-5 doses, and unvaccinated or partially vaccinated when they had received 0-3 doses of vaccine. The Chi square test and the odds ratios were used to compare percentages and the t test was used to compare mean pertussis costs in different groups, considering a p < 0.05 as statistically significant. The correlation between pertussis costs and study variables was assessed using the Spearman's ρ, with a p < 0.05 as statistically significant. Multiple linear regression analysis (IBM-SPSS program) was used to quantify the association of pertussis vaccination and other study variables with pertussis costs. RESULTS: Vaccinated children with pertussis aged 0-9 years had significantly lower odds ratios of hospitalizations (OR 0.02, p < 0.001), laboratory confirmation (OR 0.21, p < 0.001), and severe disease (OR 0.02, p < 0.001) than unvaccinated or partially vaccinated children with pertussis of the same age. Mean direct healthcare costs were significantly lower (p < 0.001) in vaccinated patients (€190.6) than in unvaccinated patients (€3550.8), partially vaccinated patients (€1116.9), and unvaccinated/partially vaccinated patients (€2330). Multivariable linear regression analysis showed that pertussis vaccination with 4-5 doses was associated with a non-significant reduction of pertussis costs of €107.9 per case after taking into account the effect of other study variables, and €200 per case after taking into account pertussis severity. CONCLUSIONS: Direct healthcare costs were lower in children with pertussis aged 0-9 years vaccinated with 4-5 doses of acellular vaccines than in unvaccinated or partially vaccinated children with pertussis of the same age.

Documento del grupo de trabajo SESPAS-OMC sobre iatrogenia / No disponible

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Is the current prevention strategy based on vaccination coverage and epidemiological surveillance sufficient to achieve measles and rubella elimination in Europe?

Elimination of measles and rubella in Europe is a feasible objective, but it requires achieving a maintaining a high prevalence of protected individuals in order to prevent cases and outbreaks from imported cases. The epidemiology of measles and rubella in Europe in the period 2003-2013 suggests that we are far away from the elimination target for measles, while the situation is better for rubella. In this situation, a new preventive strategy based on serological surveillance systems should be developed in Europe in order to identify and immunise individuals in population groups without sufficient herd immunity against measles and rubella.

The vaccination coverage required to establish herd immunity against influenza viruses.

OBJECTIVE: 1) To determine the influenza vaccination coverage required to establish herd immunity, and 2) to assess whether the percentages of vaccination coverage proposed and those registered in the United States and Europe are sufficient to establish herd immunity. METHODS: The vaccination coverage required to establish herd immunity was determined by taking into account the number of secondary cases per infected case (R(o)) and the vaccine effectiveness. RESULTS: The required percentage that would have been required to establish herd immunity against previous influenza viruses ranged from 13% to 100% for the 1918-19, 1957-58, 1968-69 and 2009-10 pandemic viruses, and from 30% to 40% for the 2008-09 epidemic virus. The objectives of vaccination coverage proposed in the United States - 80% in healthy persons and 90% in high-risk persons - are sufficient to establish herd immunity, while those proposed in Europe - only 75% in elderly and high-risk persons - are not sufficient. The percentages of vaccination coverage registered in the United States and Europe are not sufficient to establish herd immunity. CONCLUSION: The influenza vaccination coverage must be increased in the United States and Europe in order to establish herd immunity. It is necessary to develop new influenza prevention messages based on herd immunity.

Evaluation of the establishment of herd immunity in the population by means of serological surveys and vaccination coverage.

The necessary herd immunity blocking the transmission of an infectious agent in the population is established when the prevalence of protected individuals is higher than a critical value, called the herd immunity threshold. The establishment of herd immunity in the population can be determined using the vaccination coverage and seroepidemiological surveys. The vaccination coverage associated with herd immunity (V(c)) can be determined from the herd immunity threshold and vaccine effectiveness. This method requires a vaccine-specific effectiveness evaluation, and it can be used only for the herd immunity assessment of vaccinated communities in which the infectious agent is not circulating. The prevalence of positive serological results associated with herd immunity can be determined from the herd immunity threshold, in terms of prevalence of antibodies (p(c)) and serological test performance. The herd immunity is established when the prevalence of antibodies is higher than pc. This method can be used to assess the establishment of herd immunity in different population groups, both when the infectious agent is circulating and when it is not possible to assess vaccine effectiveness. The herd immunity assessment in Catalonia, Spain, showed that the additional vaccination coverage required to establish herd immunity was 3-6% for measles, mump and varicella and 11% poliovirus type III in school children, 17-59% for diphtheria in youth and adults and 25-46% for persussis in school children, youth and adults.

The cost effectiveness of statin therapies in Spain in 2010, after the introduction of generics and reference prices.

BACKGROUND: HMG-CoA reductase inhibitors (statins) are the first-line drugs for use in the reduction of low-density lipoprotein cholesterol (LDL-C) levels and prevention of coronary heart disease (CHD) in patients with hypercholesterolemia. Generic statins could change the cost effectiveness of statin therapies in Spain, and more population groups could be included in the recommendations for reduction of cholesterol levels based on cost effectiveness. OBJECTIVES: The objectives of this study were: (i) to assess the cost effectiveness of available statins for the reduction of LDL-C levels in Spain in 2010, after the introduction of generics and reference prices; (ii) to assess the cost effectiveness of combination therapy using a statin plus cholestyramine or ezetimibe; and (iii) to estimate the mean cost per patient to achieve National Cholesterol Education Program (Adult Treatment Panel-III) therapeutic objectives. METHODS: The following treatments were evaluated: rosuvastatin 5-20 mg/day; atorvastatin, simvastatin, and pravastatin 10-40 mg/day; lovastatin and fluvastatin 20-80 mg/day; and combination therapy with a statin plus either cholestyramine 12-24 g/day or ezetimibe 10 mg/day. The cost effectiveness was evaluated in terms of cost per percentage point reduction in LDL-C, comparing the annual treatment costs with the effectiveness in reducing LDL-C. Treatment costs included those for medications (2010 wholesale prices), control measures, and treatment of adverse drug effects. The effectiveness of statins was estimated by developing a meta-analysis of clinical trials published between 1993 and 2005 that met several inclusion criteria. Average and incremental cost-effectiveness ratios were calculated to assess the efficiency of individual statin and combination therapies in reducing LDL-C levels. RESULTS: The effectiveness in terms of percentage reduction in LDL-C ranged from 19% for pravastatin 10 mg/day to 55% for atorvastatin 80 mg/day. Annual treatment costs ranged from Euro 189.7 for simvastatin 10 mg/day to Euro 759.3 for atorvastatin 80 mg/day. The cost-effectiveness ratios, in terms of cost per percentage point reduction in LDL-C, were: Euro 6 for simvastatin, Euro 10-12 for rosuvastatin, Euro 10 for lovastatin, Euro 13-16 for atorvastatin, Euro 13-14 for fluvastatin, and Euro 14-20 for pravastatin. Rosuvastatin + ezetimibe, simvastatin + ezetimibe, and atorvastatin + ezetimibe were the most cost-effective combination therapies for reducing LDL-C levels. Rosuvastatin was the most cost-effective statin for achieving the LDL-C therapeutic goal in patients at high risk for CHD, with a mean cost per patient of Euro 516. Simvastatin was the most cost-effective statin to achieve the LDL-C goal in patients with moderate or low CHD risk, with a cost per patient of Euro 217 and Euro 190, respectively. CONCLUSION: Rosuvastatin should be the first-choice agent in patients with high CHD risk, while simvastatin should be the first choice in patients with moderate or low risk. The addition of ezetimibe to rosuvastatin, simvastatin, or atorvastatin should be the preferred combination therapies when greater LDL-C reductions are required. The cost effectiveness of all statin therapies has increased in Spain after the introduction of generic statins and reference prices.

Metodología y aplicabilidad de las encuestas seroepidemiológicas / Methodology and applicability of seroepidemiological surveys

Las encuestas seroepidemiológicas se definen como losestudios seroepidemiológicos desarrollados en muestraspoblacionales con el fin de investigar el nivel de proteccióninmunitario frente a enfermedades vacunables y no vacunables.En este trabajo se presenta la metodología y aplicabilidadde las encuestas seroepidemiológicas, y se discute la problemáticade los estudios seroepidemiológicos en la poblacióninmigrante. Las encuestas seroepidemiológicas se deben desarrollaren muestras representativas de la población, determinandoel tamaño muestral según el error muestral y la precisiónque se desea obtener para los parámetros poblacionales.Es necesario desarrollar un cuestionario adecuado para recogerla información sociodemográfica y médica de todos laspersonas participantes. Las técnicas serológicas deben ser sensiblesy específicas. Las encuestas seroepidemiológicas sepueden utilizar para determinar el nivel inmunitario en diferentesgrupos poblacionales y detectar las variables sociodemográficasy médicas que se asocian con la inmunidad, lavacunación y las enfermedades infecciosas(AU)

Seroepidemiological surveys can be defined as seroepidemiologicalstudies carried out in population samples to investigateimmunity levels against vaccinable and not vaccinablediseases. The objective of this paper is to present the methodologyand applicability of serological surveys. Problems relatedto seroepidemiological surveys in immigrant population arealso discussed. Seroepideniological surveys should be developedin representative samples of the population, determiningthe sample size taking into account the sample error and precisionthat should be obtained for population parameters. It isnecessary to develop an adequate questionnaire to collectsociodemographical and medical information from all participants.Serological tests should sensitive and specific. Seroepidemiologicalsurveys can be used assess immunity levels indifferent population groups, and to detect sociodemographicaland medical variables associated with the immunity, vaccinationand infectious diseases(AU9

[Methodology and applicability of seroepidemiological surveys]. / Metodología y aplicabilidad de las encuestas seroepidemiológicas.

Seroepidemiological surveys can be defined as seroepidemiological studies carried out in population samples to investigate immunity levels against vaccinable and not vaccinable diseases. The objective of this paper is to present the methodology and applicability of serological surveys. Problems related to seroepidemiological surveys in immigrant population are also discussed. Seroepideniological surveys should be developed in representative samples of the population, determining the sample size taking into account the sample error and precision that should be obtained for population parameters. It is necessary to develop an adequate questionnaire to collect sociodemographical and medical information from all participants. Serological tests should sensitive and specific. Seroepidemiological surveys can be used assess immunity levels in different population groups, and to detect sociodemographical and medical variables associated with the immunity, vaccination and infectious diseases.