Comparable diagnostic accuracy of SARS-CoV-2 Spike RBD and N-specific IgG tests to determine pre-vaccination nation-wide baseline seroprevalence in Mexico.

A major challenge for developing countries during the COVID-19 pandemic is affordable and adequate monitoring of disease progression and population exposure as the primary source relevant epidemiological indicators. Serology testing enables assessing population exposure and to guide vaccination strategies but requires rigorous accuracy validation before population-wide implementation. We adapted a two-step ELISA protocol as a single-step protocol for detection of IgG against the Receptor Binding Domain (RBD) of SARS-CoV-2 spike protein and compared its diagnostic accuracy with a commercial immunoassay anti-nucleoprotein IgG. Both methods yielded adequate and comparable diagnostic accuracy after 3 weeks post-symptom onset and were implemented in a nation-wide population based serological survey during August-November 2020. Anti-RBD National seroprevalence was 23.6%, 1.3% lower, but not significantly, than for anti-N. Double positive seroprevalence was 19.7%. Anti-N single-positive seroprevalence was 3.72% and anti-RBD single-positive seroprevalence was 1.98%. Discrepancies in the positivity to either single marker may be due to different kinetics of each antibody marker as well as the heterogeneity of the sampling time in regards to local epidemic waves. Baseline single positivity prevalence will be useful to assess the serological impact of vaccination and natural infection in further serosurveillance efforts.

Innovations in graduate public health education: the Instituto Nacional de Salud Pública.

During the past 10 years, the Instituto Nacional de Salud Pública (National Institute of Public Health) in Mexico has meticulously revised its educational model. This analysis resulted in the transformation of its educational model by tracing a new path in the pedagogical structure and faculty development to meet current challenges and students' needs. The first stage dealt with the national and international accreditation standards that came with the 21st century. The second stage responded to evidence of cognitive research showing that students are better prepared when they are engaged, active, and responsible for their own learning. This transformation was grounded on the use of information and communication technologies and on a competency-based educational approach that has led the expansion and innovation of educational practice.

Public policy for the poor? A randomised assessment of the Mexican universal health insurance programme.

BACKGROUND: We assessed aspects of Seguro Popular, a programme aimed to deliver health insurance, regular and preventive medical care, medicines, and health facilities to 50 million uninsured Mexicans. METHODS: We randomly assigned treatment within 74 matched pairs of health clusters-ie, health facility catchment areas-representing 118 569 households in seven Mexican states, and measured outcomes in a 2005 baseline survey (August, 2005, to September, 2005) and follow-up survey 10 months later (July, 2006, to August, 2006) in 50 pairs (n=32 515). The treatment consisted of encouragement to enrol in a health-insurance programme and upgraded medical facilities. Participant states also received funds to improve health facilities and to provide medications for services in treated clusters. We estimated intention to treat and complier average causal effects non-parametrically. FINDINGS: Intention-to-treat estimates indicated a 23% reduction from baseline in catastrophic expenditures (1.9% points; 95% CI 0.14-3.66). The effect in poor households was 3.0% points (0.46-5.54) and in experimental compliers was 6.5% points (1.65-11.28), 30% and 59% reductions, respectively. The intention-to-treat effect on health spending in poor households was 426 pesos (39-812), and the complier average causal effect was 915 pesos (147-1684). Contrary to expectations and previous observational research, we found no effects on medication spending, health outcomes, or utilisation. INTERPRETATION: Programme resources reached the poor. However, the programme did not show some other effects, possibly due to the short duration of treatment (10 months). Although Seguro Popular seems to be successful at this early stage, further experiments and follow-up studies, with longer assessment periods, are needed to ascertain the long-term effects of the programme.

Chapter 27: Research needs following initial licensure of virus-like particle HPV vaccines.

Human papillomavirus virus-like particle (HPV VLP) HPV vaccines currently evaluated for licensing are likely to be available soon. Licensure will be based on evidence that the vaccine is well tolerated and provides near complete type-specific protection against HPV infections and their resulting lesions in the first few years after vaccination. Several important questions will remain to be answered after licensure to guide vaccine implementation and to permit the rational evaluation of vaccination in cancer prevention programs. These include the long-term safety and efficacy of vaccination, the optimal ages for vaccination, efficacy against HPV types not included in the vaccine and against existing infections, and efficacy in males. Modulators of vaccine efficacy (e.g., HIV infection) and immune mechanisms of long-term protection also remain to be defined. The real-world effectiveness of vaccination programs will need to be assessed. Issues related to the implementation of a vaccine that targets pre-adolescents and early adolescents and to the acceptability of a cancer vaccine targeted against a sexually transmitted infection will need to be understood before vaccination programs can be successful. It is hoped that continued improvements to the current HPV vaccines will lead to the introduction in future years of second generation vaccines that simplify delivery and/or expand its coverage. Finally, the natural history of HPV types not covered in the candidate vaccines will need to be carefully studied following vaccination. Public health authorities in various countries will play a pivotal role in determining if these questions are answered in a timely manner.

Reduced seminal parameters associated with environmental DDT exposure and p,p'-DDE concentrations in men in Chiapas, Mexico: a cross-sectional study.

In response to mounting concerns about the endocrine-disrupting influence of environmental chemicals on human health, this epidemiological study was initiated to test the hypothesis that nonoccupational exposure to the estrogenic pesticide 1,1,1-trichloro-2,2-bis(chlorodiphenyl)ethane (DDT) affects male reproductive parameters. One hundred and sixteen men aged 27 years (SD = 8.2) living in malaria endemic-areas in Chiapas (Mexico), where DDT was sprayed until 2000, participated in a cross-sectional study. Semen analyses were conducted according to World Health Organization methods and a quality control program was followed. DDT exposure was defined as the level of blood plasma p,p'-dichlorodiphenyl dichloroethylene (DDE), the major metabolite of DDT. The p,p'-DDE concentration adjusted for total lipids was 100 times higher than that reported for nonexposed populations at 45 plus or minus 32 mug/g (mean +/- SD). Crude regression analysis showed that several sperm motion parameters, including the percentage of motile sperm, decreased with higher p,p'-DDE concentrations (beta = -8.38; P = .05 for squared motility), and the percentage of sperm with morphological tail defects increased with higher plasma p,p'-DDE concentration (beta = 0.003; P = .017). Insufficient sperm chromatin condensation was observed in 46.6% of participants, and the most severe category of incomplete DNA condensation was also positively correlated with p,p'-DDE concentration (r = .223; P = .044). Therefore, nonoccupational exposure to DDT, as assessed by plasma p,p'-DDE concentrations, is associated with poorer semen parameters in men, indicating adverse effects on testicular function and/or the regulation of reproductive hormones. Previously, a causal role of environmental toxicants in human male infertility has been lacking because observed effects have been the result of unusually high exposures, either occupationally or as a result of industrial accidents, resulting in unprecedented controversy (reviewed by Cheek & McLachlan, Environmental hormones and the male reproductive system. J Androl. 1998;19:5). This is the first epidemiological study demonstrating effects after nonoccupational exposures to DDT. Based on these findings, the effect of DDT on male reproductive health should not be ignored.

Microalbuminuria as a predictor of myocardial infarction in a Mexican population: the Mexico City Diabetes Study.

OBJECTIVE: Our objective was to evaluate whether microalbuminuria predicts myocardial infarction (MI) in a Mexican population. METHODS: The study was a prospective, population-based cohort. Baseline examination was carried out in 1989; the first follow-up in 1993 and the second in 1997. All men and non-pregnant women between 35 and 64 years of age at the start of the study were considered eligible. Clinical, anthropometric, and laboratory characteristics were evaluated. All patients with macroalbuminuria at baseline were excluded from the present analyses, as were all prevalent cases with MI. Remaining patients were classified as with or without microalbuminuria. Incident cases of MI were identified during follow-up phases using an electrocardiogram (according to the Minnesota Code) or the death certificate (in which underlying cause of death was listed as MI, Causes of Death codes 410.0-410.9). Results. From 2196 individuals, 1586 satisfied the inclusion criteria. Two hundred fifteen (13.6%) had microalbuminuria, and 1371 (86.4%) did not. During follow-up, 10 patients with microalbuminuria and 31 patients without microalbuminuria developed an MI. Using robust logistic regression, the probability of developing MI, adjusting by Framingham score, was estimated to be 1.90 (95% CI,.97-3.72) times higher in patients with microalbuminuria as compared with patients without microalbuminuria. CONCLUSION: We found that in a Mexican population the relationship between microalbuminuria and incidence of MI was borderline statistically significant after adjusting for other cardiovascular risk factors.