Pertussis in Mexico from 2000 to 2019: A real-world study of incidence, vaccination coverage, and vaccine effectiveness

BACKGROUND

The national immunization program in Mexico includes a 3-dose primary series of pertussis vaccine and a toddler booster dose. In Mexico, whole-cell pertussis vaccines (wP) were switched in 2007 to acellular pertussis vaccines (aP).

METHODS

This retrospective study using Mexican National Databases of Health and population surveillance (2000-2019) assessed the incidence of pertussis, infant pertussis vaccination coverage, and vaccine effectiveness (VE) against clinically-diagnosed and/or laboratory-confirmed pertussis in children aged 6.5-18.5 or 24.5 months for the primary series, and children aged 18.5 or 24.5-48.5 months for the toddler booster.

RESULTS

The incidence of pertussis sharply increased in 2012 and was highest in 2012, 2015, and 2016 (0.84-0.94/100,000 person-years). Coverage was highest for the first dose in the primary series, decreasing for each subsequent dose. The VE against notified pertussis was 96.4% (95% CI: 94.7, 97.6) for the first three doses of wP vaccine (2000-2007) and 95.7% (95% CI: 95.1, 96.2) for the first three doses of aP vaccine (2008-2019).

CONCLUSIONS

Our findings suggested high levels of vaccine effectiveness overall were achieved for the aP and wP vaccines in Mexico between 2000 and 2019.

Mathematical modeling of Dengue virus serotypes propagation in Mexico

The Dengue virus (DENV) constitutes a major vector borne virus disease worldwide. Prediction of the DENV spread dynamics, prevalence and infection rates are crucial elements to guide the public health services effort towards meaningful actions. The existence of four DENV serotypes further complicates the virus proliferation forecast. The different serotypes have varying clinical impacts, and the symptomatology of the infection is dependent on the infection history of the patient. Therefore, changes in the prevalent DENV serotype found in one location have a profound impact on the regional public health. The prediction of the spread and intensity of infection of the individual DENV serotypes in specific locations would allow the authorities to plan local pesticide spray to control the vector as well as the purchase of specific antibody therapy. Here we used a mathematical model to predict serotype-specific DENV prevalence and overall case burden in Mexico.

Exposición a radiación ionizante en médicos residentes de ortopedia en un hospital de referencia

OBJECTIVE

To describe and analyze the exposure to ionizing radiation of orthopedic residents.

METHOD

A prospective study was carried out to evaluate the degree of exposure to ionizing radiation with a bandage dosimeter placed under the lead apron for medical residents for 10 months. An online survey measured the degree of knowledge about radiation safety.

RESULTS

54 resident physicians participated. 55.6% report having knowledge of the existence of radiological protection equipment and 40.7% report that they had previous training in its use. 77.8% use the leaded apron and 31.5% use thyroid protection. 81.5% were positioned less than 1 meter from the source of the X-ray production of the arc in C. The total mean radiation exposure was 2.9 ± 2.17 mSv (95% confidence interval: 1.25-14.28; p = 0.424).

CONCLUSIONS

Orthopedic residents present radiation doses below the International Commission on Radiological Protection recommended limit. However, there is a lack of knowledge of radiation protection and as well as a lack of interest and ignorance of the adverse effects of radiation.

Burden of disease and associated complications of hepatitis a in children and adults in Mexico: A retrospective database study

BACKGROUND

Hepatitis A virus (HAV) infection is a leading cause of viral hepatitis in children, yet the HAV vaccine is not included in the national immunization program (NIP) in Mexico. This study addresses an identified evidence gap of the burden of hepatitis A disease, complications, and associated costs in Mexico by analyzing surveillance and healthcare data. Data review included disease morbidity (incidence and hospitalization), mortality, and healthcare resource utilization costs.

METHODS

In this observational, retrospective database study, we conducted a systematic screening, extraction, and analysis of outcome data from the national surveillance system in Mexico from January 2000 to December 2019.

RESULTS

During the analysis period (2000-2019), the average incidence rate/year of HAV cases was 14.7 (5.4-21.5) per 100,000 inhabitants. Children 1-9 years of age (YoA) had the highest average incidence rate/year with 47.8 (14.7-74.5). The average hospitalization rate/year due to HAV infection was 5.8% (2.9-9.6%). Although the highest burden of HAV continued to be in children (1-9 YoA), an increase in incidence and hospitalizations (with complications) in older age groups (≥ 10-64 YoA) was observed. The annual average fatality rate was estimated to be 0.44% (0.26-0.83%) of which 28.8% of deaths were concentrated in adults ≥ 65 YoA. The total direct costs of medical attention due to HAV and related complications were estimated at $382 million Mexican pesos.

CONCLUSION

The overall results suggest an uptrend in HAV infections in adolescents/adults compared to children in Mexico. Therefore, as the overall incidence risk of HAV infection decreases, the mean age of infection increases. This consequently increases the risk of severity and complications in older age groups, thus increasing the demand for healthcare resources. Our findings provide evidence for including the inactivated HAV vaccine in the Mexican NIP.

Probability of consolidation constrains novel serotype emergence in dengue fever virus

Since their first sequencing 40 years ago, Dengue virus (DENV) genotypes have shown extreme coherence regarding the serotype class they encode. Considering that DENV is a ribonucleic acid (RNA) virus with a high mutation rate, this behavior is intriguing. Here, we explore the effect of various parameters on likelihood of new serotype emergence. In order to determine the time scales of such an event, we used a Timed Markov Transmission Model to explore the influences of sylvatic versus peri-urban transmission, viral mutation rate, and vertical transmission on the probabilities of novel serotype emergence. We found that around 1 000 years are required for a new serotype to emerge, consistent with phylogenetic analysis of extant dengue serotypes. Furthermore, we show that likelihood of establishing chains of mosquito-human-mosquito infection, known as consolidation, is the primary factor which constrains novel serotype emergence. Our work illustrates the restrictions on and provides a mechanistic explanation for the low probability of novel dengue virus serotype emergence and the low number of observed DENV serotypes.

Pertussis infant morbidity and mortality trends after universal maternal immunisation in Mexico: An ecological database study with time-series analysis

INTRODUCTION

Pertussis is a highly contagious infectious disease caused by Bordetella pertussis and a leading cause of infant mortality in Mexico. The Tetanus-diphtheria-acellular pertussis (Tdap) vaccine was recommended in the Mexican Immunisation Programme for pregnant women in 2013. We describe pertussis morbidity and mortality trends in infants ≤2 and ≤12 months of age), before and after maternal Tdap immunisation implementation in Mexico.

METHODS

An ecological retrospective database study was performed in the Mexican National and Workers Social Security Institutes (IMSS; ISSSTE). Data were collected on confirmed pertussis ambulatory cases, hospitalisations, and deaths, plus vaccination coverage (Tdap; Diphtheria-tetanus-acellular pertussis [DTPa]) and population estimates. Descriptive and regression time-trend analyses were performed for pertussis morbidity and mortality in infants between pre- (2010-2012) and post- (2014-2018) maternal Tdap immunisation periods.

RESULTS

Around 1 million infants a year are covered in IMSS/ISSSTE databases. Average full primary infant DTPa vaccine coverage was 71.4%-72.7% nationally. Since 2013, annual maternal Tdap vaccine coverage ranged from 70%-93%. Between 2010-2018, 2,024 pertussis cases, 2,518 hospitalisations and 71 deaths were reported in infants. Among infants 0-2 months old (maternal immunisation target group), there was a significant decrease, post-maternal vaccination, in pertussis incidence (49.9%, p < 0.000), hospitalisation (70.0%, p < 0.000) and mortality (82.4%, p = 0.003). In infants 0-12 months old, pertussis hospitalisations (28.9%, p = 0.000) and mortality (36.2%, p = 0.059) decreased, but incidence increased (61.8%, p = 0.000).

CONCLUSION

After maternal immunisation was implemented, there was a decreasing trend in incidence, hospitalisation and death due to pertussis in infants 0-2 months old. Increases in incidence reported in 0-12-month-olds are likely due to major changes in diagnosis and reporting introduced during the study period as well as limited vaccination and health coverage in some states. These findings confirm the important contribution of the Tdap maternal immunisation programme in reducing pertussis disease burden, particularly severe disease, among infants in Mexico.

Vaccine coverage and compliance in Mexico with the two-dose and three-dose rotavirus vaccines

Worldwide, rotavirus infection has been a leading cause of severe diarrhea morbidity and mortality. Two rotavirus vaccines have been used in the National Immunization Program (NIP) in Mexico; two-dose Rotarix from 2006 to 2011 and three-dose RotaTeq since 2011. This study assessed coverage (receiving at least one dose or full dose series) in eligible infants, compliance (% completing dose series and % completing series on schedule) in eligible infants vaccinated with Rotarix (2010) versus RotaTeq (2012), using Mexican Social Security Institute data nationwide and by regions. In 2010, 80.7% received at least one dose of Rotarix, 75.6% received both doses and 57.0% received both doses on schedule. In 2012, 85.7% received at least one dose of RotaTeq, 61.0% received all three doses and 43.2% received all three doses on schedule. More eligible infants received all doses with Rotarix versus RotaTeq (p < 0.001). Among infants vaccinated with Rotarix versus RotaTeq, 93.7% versus 71.1% completed full series (p < 0.001), and 75.5% versus 70.9% completed full series on schedule (p = 0.105), respectively. The full series coverage and compliance decreased in all regions with RotaTeq compared with Rotarix. In conclusion, rotavirus vaccination has successfully reduced morbidity and mortality in children under 5 years in Mexico. This study found significant differences in full series coverage and compliance among infants and a higher proportion of completed scheduled at an earlier age in Mexico when comparing a two-dose vaccine in 2010 with a three-dose vaccine in 2012. Such differences might need to be taken into consideration to maximize NIP benefits, including early protection of the rotavirus vaccination program.

Prediction of dengue outbreaks in Mexico based on entomological, meteorological and demographic data

Dengue virus has shown a complex pattern of transmission across Latin America over the last two decades. In an attempt to explain the permanence of the disease in regions subjected to drought seasons lasting over six months, various hypotheses have been proposed. These include transovarial transmission, forest reservoirs and asymptomatic human virus carriers. Dengue virus is endemic in Mexico, a country in which half of the population is seropositive. Seropositivity is a risk factor for Dengue Hemorrhagic Fever upon a second encounter with the dengue virus. Since Dengue Hemorrhagic Fever can cause death, it is important to develop epidemiological mathematical tools that enable policy makers to predict regions potentially at risk for a dengue epidemic. We formulated a mathematical model of dengue transmission, considering both human behavior and environmental conditions pertinent to the transmission of the disease. When data on past human population density, temperature and rainfall were entered into this model, it provided an accurate picture of the actual spread of dengue over recent years in four states (representing two climactic conditions) in Mexico.

The cost-effectiveness of treating triple coinfection with HIV, tuberculosis and hepatitis C virus

OBJECTIVES

The objective of this study was to estimate the cost-effectiveness of treating patients infected with HIV and simultaneously coinfected with tuberculosis (TB) and hepatitis C virus (HCV).

METHODS

A mathematical model for HIV coinfection with TB and HCV is introduced. The model was designed to incorporate parameters of control for the coverage of care, which makes it useful for performing cost-effectiveness analysis of public policies. A cost-effectiveness analysis of early medical care of patients with TB and HCV coinfection, with coverage of 0 (basal), 25, 50, 75 and 100%, was performed for the whole cohort of patients and a special analysis was performed in a selected population with triple infection.

RESULTS

The cost per resolved infection and the cost per year of life gained were found to be very cost-effective for the population with triple infection, for all different coverages.

CONCLUSIONS

It is known that treating patients with HIV who are coinfected with TB or HCV implies high cost and low efficacy, but it is possible that the population with triple infections could achieve important benefits in terms of years of life gained.

Cost-Effectiveness of Blood Donation Screening for Trypanosoma cruzi in Mexico

An estimated 2 million inhabitants are infected with Chagas disease in Mexico, with highest prevalence coinciding with highest demographic density in the southern half of the country. After vector-borne transmission, Trypanosoma cruzi is principally transmitted to humans via blood transfusion. Despite initiation of serological screening of blood donations or donors for T. cruzi since 1990 in most Latin American countries, Mexico only finally included mandatory serological screening nationwide in official Norms in 2012. Most recent regulatory changes and segmented blood services in Mexico may affect compliance of mandatory screening guidelines. The objective of this study was to calculate the incremental cost-effectiveness ratio for total compliance of current guidelines from both Mexican primary healthcare and regular salaried worker health service institutions: the Secretary of Health and the Mexican Institute for Social Security. We developed a bi-modular model to analyze compliance using a decision tree for the most common screening algorithms for each health institution, and a Markov transition model for the natural history of illness and care. The incremental cost effectiveness ratio based on life-years gained is US$ 383 for the Secretary of Health, while the cost for an additional life-year gained is US$ 463 for the Social Security Institute. The results of the present study suggest that due to incomplete compliance of Mexico’s national legislation during 2013 and 2014, the MoH has failed to confirm 15,162 T. cruzi infections, has not prevented 2,347 avoidable infections, and has lost 333,483 life-years. Although there is a vast difference in T. cruzi prevalence between Bolivia and Mexico, Bolivia established mandatory blood screening for T.cruzi in 1996 and until 2002 detected and discarded 11,489 T. cruzi -infected blood units and prevented 2,879 potential infections with their transfusion blood screening program. In the first two years of Mexico’s mandated program, the two primary institutions failed to prevent due to incomplete compliance more potential infections than those gained from the first five years of Bolivia’s program. Full regulatory compliance should be clearly understood as mandatory for the sake of blood security, and its monitoring and analysis in Mexico should be part of the health authority’s responsibility.

Chagas disease continues to be a neglected disease in Mexico and Latin-American. Although an estimated 96% of Trypanosoma cruzi transmission to humans occurs via 32 triatomine vector species, the only transmission prevention in Mexico has been sparse and based on heterogeneous blood donation screening. Despite mandating serological screening of blood donations or donors for T. cruzi since 1990 in most Latin American countries, Mexico only finally included mandatory serological screening nationwide in official Norms in 2012. In 2005, a survey of blood donor centers in Mexico was conducted to compare T. cruzi prevalence in donations with that of Mexican migrants in the US. Since there was little coincidence between data from that survey and official screening or confirmed case rates, and screening for the social security system only initiated in 2010, the objective of this study was to calculate the incremental cost-effectiveness ratio for total compliance of current guidelines from both Mexican primary healthcare (the Secretary of Health) and regular salaried worker health services (the Mexican Institute for Social Security). A bi-modular model to analyze compliance was developed using a decision tree for the most common documented screening algorithms for the two principal health institution, and a Markov transition model for the natural history of illness and care. The incremental cost effectiveness ratio based on life-years gained is US$ 383 for the Secretary of Health (MoH), while the cost for an additional life-year gained is US$ 463 for the Social Security Institute (IMSS). Using survey compliance data for MoH, and that published by IMSS, failure to detect current infections, to avoid new infections, and life-years lost were calculated for 2013 and 2014 for both institutions. The MoH has failed to confirm 15,162 T. cruzi infections, did not prevent 2,347 avoidable infections, and lost 333,483 life-years over the two year period. Full regulatory compliance should be mandatory and timely monitoring should be part of the health authority’s responsibilities for the sake of blood security in Mexico.

Lower IgG somatic hypermutation rates during acute dengue virus infection is compatible with a germinal center-independent B cell response

BACKGROUND

The study of human B cell response to dengue virus (DENV) infection is critical to understand serotype-specific protection and the cross-reactive sub-neutralizing response. Whereas the first is beneficial and thus represents the ultimate goal of vaccination, the latter has been implicated in the development of severe disease, which occurs in a small, albeit significant, fraction of secondary DENV infections. Both primary and secondary infections are associated with the production of poly-reactive and cross-reactive IgG antibodies.

METHODS

To gain insight into the effect of DENV infection on the B cell repertoire, we used VH region high-throughput cDNA sequencing of the peripheral blood IgG B cell compartment of 19 individuals during the acute phase of infection. For 11 individuals, a second sample obtained 6 months later was analyzed for comparison. Probabilities of sequencing antibody secreting cells or memory B cells were estimated using second-order Monte Carlo simulation.

RESULTS

We found that in acute disease there is an increase in IgG B cell diversity and changes in the relative use of segments IGHV1-2, IGHV1-18, and IGHV1-69. Somewhat unexpectedly, an overall low proportion of somatic hypermutated antibody genes was observed during the acute phase plasmablasts, particularly in secondary infections and those cases with more severe disease.

CONCLUSIONS

Our data are consistent with an innate-like antiviral recognition system mediated by B cells using defined germ-line coded B cell receptors, which could provide a rapid germinal center-independent antibody response during the early phase of infection. A model describing concurrent T-dependent and T-independent B cell responses in the context of DENV infection is proposed, which incorporates the selection of B cells using hypomutated IGHV segments and their potential role in poly/cross-reactivity. Its formal demonstration could lead to a definition of its potential implication in antibody-dependent enhancement, and may contribute to rational vaccine development efforts.

Radiographers supporting radiologists in the interpretation of screening mammography: a viable strategy to meet the shortage in the number of radiologists

BACKGROUND

An alternative approach to the traditional model of radiologists interpreting screening mammography is necessary due to the shortage of radiologists to interpret screening mammograms in many countries.

METHODS

We evaluated the performance of 15 Mexican radiographers, also known as radiologic technologists, in the interpretation of screening mammography after a 6 months training period in a screening setting. Fifteen radiographers received 6 months standardized training with radiologists in the interpretation of screening mammography using the Breast Imaging Reporting and Data System (BI-RADS) system. A challenging test set of 110 cases developed by the Breast Cancer Surveillance Consortium was used to evaluate their performance. We estimated sensitivity, specificity, false positive rates, likelihood ratio of a positive test (LR+) and the area under the subject-specific Receiver Operating Characteristic (ROC) curve (AUC) for diagnostic accuracy. A mathematical model simulating the consequences in costs and performance of two hypothetical scenarios compared to the status quo in which a radiologist reads all screening mammograms was also performed.

RESULTS

Radiographer's sensitivity was comparable to the sensitivity scores achieved by U.S. radiologists who took the test but their false-positive rate was higher. Median sensitivity was 73.3 % (Interquartile range, IQR: 46.7-86.7 %) and the median false positive rate was 49.5 % (IQR: 34.7-57.9 %). The median LR+ was 1.4 (IQR: 1.3-1.7 %) and the median AUC was 0.6 (IQR: 0.6-0.7). A scenario in which a radiographer reads all mammograms first, and a radiologist reads only those that were difficult for the radiographer, was more cost-effective than a scenario in which either the radiographer or radiologist reads all mammograms.

CONCLUSIONS

Given the comparable sensitivity achieved by Mexican radiographers and U.S. radiologists on a test set, screening mammography interpretation by radiographers appears to be a possible adjunct to radiologists in countries with shortages of radiologists. Further studies are required to assess the effectiveness of different training programs in order to obtain acceptable screening accuracy, as well as the best approaches for the use of non-physician readers to interpret screening mammography.

A beta-complex statistical four body contact potential combined with a hydrogen bond statistical potential recognizes the correct native structure from protein decoy sets

We present a new four-body knowledge-based potential for recognizing the native state of proteins from their misfolded states. This potential was extracted from a large set of protein structures determined by X-ray crystallography using BetaMol, a software based on the recent theory of the beta-complex (β-complex) and quasi-triangulation of the Voronoi diagram of spheres. This geometric construct reflects the size difference among atoms in their full Euclidean metric; property not accounted for in a typical 3D Delaunay triangulation. The ability of this potential to identify the native conformation over a large set of decoys was evaluated. Experiments show that this potential outperforms a potential constructed with a classical Delaunay triangulation in decoy discrimination tests. The addition of a statistical hydrogen bond potential to our four-body potential allows a significant improvement in the decoy discrimination, in such a way that we are able to predict successfully the native structure in 90% of cases.