Decreasing vaccine coverage rates lead to increased vulnerability to the importation of vaccine-preventable diseases in Brazil

The maintenance of high vaccine coverage is an important strategy for infectious diseases control in the context of increased global travel due to migration and tourism, especially for emerging economies, which are now destinations for ~44.5% of international travellers.1 In this issue of the Journal of Travel Medicine, Tuite et al. describe the vulnerable socioeconomic condition of Venezuela and consequent massive migration to neighbouring countries (in particular Colombia, Ecuador and Brazil).2 In their study, the authors synthesized data on recent infectious disease events in Venezuela and among international migrants from Venezuela. By using passenger-level itinerary data from the International Air Transport Association to evaluate trends in outbound air travel from Venezuela over time, they applied various mobility models (including radiation and impedance models), to estimate the expected population flows from Venezuelan cities to other major Latin American and Caribbean cities. The re-emergence of infectious diseases previously controlled or eliminated in Venezuela correlates with the collapse of national public healthcare system, and highlights the potential for the exportation of these infectious diseases to countries receiving such migrants. As outbreaks of measles, diphtheria and malaria have been reported across Venezuela and other diseases, such as HIV and tuberculosis, are resurgent, such diseases can easily spread to neighbouring countries such as Brazil. Despite the free delivery and administration of vaccines in Brazil, child vaccination coverage has steadily declined in all Brazilian states since 2016. For example, coverage of the first dose of measles/mumps/rubella (MMR) has decreased substantially in two regions of Brazil: Northeastern (from 55.8% to 41.9%) and in the North (from 58.9% to 44.9%).3 The increased flow of Venezuelan immigrants into the Brazil, therefore, presents a considerable risk to Brazilian children because the mean MMR coverage is only 46.7% in Brazil.3 As a consequence of the low-vaccine coverage rate and the introduction of measles via Venezuelan immigrants, in the State of Amazonas—an important entry route into Brazil for Venezuelans—a measles outbreak occurred with 1.358 confirmed cases of measles (1.087 in Manaus, its capital city) and another 7.711 cases under investigation by September 2018.3 No measles deaths have been reported in the Amazonas over the past 18 years; however, on July 2018, the first death due to measles in a newborn was confirmed by the Central Public Health Laboratory of the Amazonas.4 Two other measles deaths were reported in the Amazonas since July. Other Brazilian states have reported cases of measles including Roraima (Northern Region, located on the border with Venezuela, which reported 310 positive cases, 4 deaths and 54 cases are still under investigation), São Paulo (2 cases), Rio de Janeiro (18 cases); Rio Grande do Sul (24 cases); Rondônia (2 cases), Pernambuco (4 cases), Pará (2 cases) and Sergipe (4 cases).3 Measles remains a continuous threat for travellers, as also evidenced in the GeoSentinel network of travel medicine providers.5 Furthermore, polio has seen a recent resurgence through travellers.6 The potential resurgence of polio in Venezuela due to its low-vaccine coverage poses a threat to Brazil. In Brazil, polio vaccine coverage by August 2018 was considered low with a national mean value—72.9%; this presents a potential condition with a considerable risk of the child population being unprotected.7 The Brazilian Ministry of Health attempted to improve coverage with a recent vaccination campaign (MMR and poliomyelitis), but despite reaching 95% of expected coverage in the target population (children aged 12 months through 12 years), it was not homogeneous and the critical regions did not reach a high level of vaccine coverage. There are many reasons for the decreasing vaccine coverage in Brazil including misinformation about the importance of vaccines and administration schedule and vaccine hesitancy (also a common problem in developed nations).8 The increasing number of anti-vaccination groups, fake news and conspiracy theories against immunization are current concerns for vaccine coverage maintenance.9 A study of Canadian parents in 2010, for example, found that the majority of respondents (65% of mothers/72% of fathers) believed that the MMR vaccine is unsafe or probably causes autism.10 Underfunding of the Brazilian public health system with continuous reduction in its annual budget, absence of effective leadership in the Ministry of Health, abandonment of disease prevention campaigns and other important preventive public health policies are additional important reasons for the poor vaccine coverage rates. We recommend the maintenance of public vaccination campaigns to improve the coverage in this period of influx of migrants and refugees from Venezuela. Urgent measures should include increasing vaccine coverage rates, and the use of vaccine-preventable disease serology as a screening tool to identify patients in need of vaccination.11 Furthermore, implementing screening and vaccination programs for incoming migrants from Venezuela should be intensified. Predicting where international migrants are relocating to is critical, given the association between human mobility and the spread of infectious diseases combined with the vulnerability of receiving countries. Simple models can be useful for providing insights into population mobility and may help identify areas likely to receive a large number of migrants.2 Using locally derived seroprevalence data on vaccine-preventable diseases by birth cohort to determine risks for vaccine-preventable diseases will help identify high-risk areas that are particularly vulnerable to the importation of vaccine-preventable diseases.12 The authors wish to acknowledge the assistance of the Instituto de Medicina Tropical de São Paulo, Federal Institute of Education, Science and Technology of São Paulo and CAPES. Conflict of interest: None declared.