Influenza vaccination in Brazil: rationale and caveats

Inactivated trivalent influenza vaccination is associated with lower mortality among patients with COVID-19 in Brazil

OBJECTIVE

To estimate associations between trivalent influenza vaccination and COVID-19 mortality as well as severe clinical outcomes among hospitalised patients.

DESIGN

Retrospective observational study.

SETTING

This study was conducted among hospitalised patients with COVID-19 in Brazil.

PARTICIPANTS

We analysed all hospitalised patients with COVID-19 with available vaccination information captured in Brazil's national electronic respiratory infection data system between 1 January 2020 and 23 June 2020.

MAIN OUTCOME MEASURES

The primary outcomes were age-specific mortality rates of hospitalised patients with COVID-19 with and without recent inactivated trivalent influenza vaccination.

RESULTS

A total of 53 752 clinically confirmed COVID-19 cases were analysed. Controlling for health facility of treatment, comorbidities as well as an extensive range of sociodemographic factors, patients who received a recent influenza vaccine experienced on average 7% lower odds of needing intensive care treatment (95% CI 0.87 to 0.98), 17% lower odds of requiring invasive respiratory support (95% CI 0.77 to 0.88) and 16% lower odds of death (95% CI 0.78 to 0.90). Protective effects were larger when the vaccine was administered after onset of symptoms as well as among younger patients.

CONCLUSION

Patients with COVID-19 with recent inactivated influenza vaccination experience significantly better health outcomes than non-vaccinated patients in Brazil. Beneficial off-target effects of influenza vaccination through trained innate immune responses seem plausible and need to be further explored. Large-scale promotion of influenza vaccines seems advisable, especially in populations at high risk for severe COVID-19 disease progression.

Age and Location in Severity of COVID-19 Pathology: Do Lactoferrin and Pneumococcal Vaccination Explain Low Infant Mortality and Regional Differences?

Two conundrums puzzle COVID-19 investigators: 1) morbidity and mortality is rare among infants and young children and 2) rates of morbidity and mortality exhibit large variances across nations, locales, and even within cities. It is found that the higher the rate of pneumococcal vaccination in a nation (or city) the lower the COVID-19 morbidity and mortality. Vaccination rates with Bacillus Calmette-Guerin, poliovirus, and other vaccines do not correlate with COVID-19 risks, nor do COVID-19 case or death rates correlate with number of people in the population with diabetes, obesity, or adults over 65. Infant protection may be due to maternal antibodies and antiviral proteins in milk such as lactoferrin that are known to protect against coronavirus infections. Subsequent protection might then be conferred (and correlate with) rates of Haemophilus influenzae type B (Hib) (universal in infants) and pneumococcal vaccination, the latter varying widely by geography among infants, at-risk adults, and the elderly. Also see the video abstract here https://youtu.be/GODBYRbPL00.

Global Influenza Hospital-based Surveillance Network (GIHSN): results of surveillance of influenza and other respiratory viruses in hospitalised patients in Brazil, 2015

BACKGROUND

Influenza-like illness occurs annually worldwide, with peak timing and severity varying seasonally, resulting in significant annual mortality.

OBJECTIVES

There were three objectives: (1) to describe the epidemiological and clinical features of hospitalised patients with severe acute respiratory infection caused by influenza and other respiratory viruses (ORVs); (2) to report the influenza seasonality in the region and (3) to correlate findings of influenza circulation and immunisation time in Brazil.

PATIENTS/METHODS

This study took place in three Brazilian hospitals located in cities with different climatic conditions (Curitiba (south), Rio de Janeiro (south-east) and Fortaleza (north-east)). Patients presenting with an acute process with indication for admission consisting of a predefined set of conditions potentially associated with recent influenza infection were enrolled.

RESULTS

We screened 1666 patients, with 595 meeting the inclusion criteria. Influenza viruses and ORVs were detected in 6.5% and 59% of patients, respectively. Influenza-positive cases fell into the severe spectrum as compared with those with ORVs (30% vs 11%), but without any difference in mortality rates. Epidemiological results revealed variations in the peak time of influenza infections between north-east (Fortaleza) and south (Curitiba) Brazil, basically following the rain period of each region. In north-east Brazil, viral circulation was prevalent in the first 4 months of the year, indicating that the vaccination campaign occurred in a postseasonal period, possibly explaining the low effectiveness.

CONCLUSIONS

The active-surveillance model is a valuable tool for investigating respiratory virus impact on hospitalised patients, with influenza-infection monitoring enabling implementation of adequate preventive measures.

Considerations of strategies to provide influenza vaccine year round

There is potential for influenza vaccine programmes to make a substantial impact on severe disease in low-resource settings, however questions around vaccine composition and programmatic issues will require special attention. Some countries may benefit from immunization programmes that provide year-round supply of vaccine; however the best way to ensure adequate vaccine supply has yet to be determined. In this report, we discuss vaccine composition, availability, and programmatic issues that must be considered when developing year-round influenza immunization programmes. We then explore how these considerations have influenced immunization practices in the Latin American region as a case study. We identify three different approaches to achieve year-round supply: (1) alternating between Northern Hemisphere and Southern Hemisphere formulations, (2) extending the expiration date to permit extended use of a single hemisphere formulation, and (3) local vaccine manufacture with production timelines that align with local epidemiology. Each approach has its challenges and opportunities. The growing data suggesting high influenza disease burden in low resource countries underscores the compelling public health need to determine the best strategies for vaccine delivery.

2010 A(H1N1) vaccination in pregnant women in Brazil: identifying coverage and associated factors

We studied vaccination coverage and its associated factors in the 2010 pandemic influenza vaccination of Brazilian pregnant women. A cross-sectional study of pregnant women who had given birth was performed in a municipality in southern Brazil, in 2010. Data about vaccination against A(H1N1) and sociodemographic characteristics, morbidities and prenatal care were collected. Statistical analysis was performed using a Poisson regression. Coverage was 77.4%. Most were vaccinated in the public sector (97.6%) and in the second trimester (47%). Associated factors that increased vaccination were marriage, older age, first income quartile, prenatal care and influenza before pregnancy. Education and skin color were not significantly associated with vaccination. The vaccination campaign was extensive and exhibited no inequality. Prenatal care was the factor that most affected vaccination coverage, reflecting its importance for vaccination campaign success.

Ecological study on mortality from influenza and pneumonia before and after influenza vaccination in the Northeast and South of Brazil

The study compared mortality from influenza and pneumonia in elderly people (65 years or older) before and since implementation of influenza vaccination in the South and Northeast regions of Brazil. Official population and mortality data were retrieved from government agencies to estimate weekly mortality rates. The Serfling model was used to identify influenza outbreaks and estimate the mortality attributable to them. In the South, the vaccination period showed a major reduction in mortality from influenza and pneumonia and in the number and duration of influenza outbreaks. These results were interpreted as consistent with the hypothesis of the vaccination program's effectiveness. In the Northeast, there was an increase in mortality from influenza and pneumonia during vaccination, which was associated with a quality improvement in recording causes of death in the elderly. An increase was also seen in mortality attributable to influenza outbreaks, suggesting a mismatch between the period in which vaccination is conducted and the relevant climatic characteristics for influenza transmission.

Effectiveness of the Brazilian influenza vaccination policy, a systematic review

Since 1999, Brazil has undertaken annual influenza vaccine campaigns, free of charge, targeting the elderly population, health professionals, and immune-deficient patients. We conducted a systematic review of literature in order to evaluate the effectiveness of the initiative. We used the keywords influenza, vaccine, Brazil and effectiveness to search the main databases. Thirty-one studies matched our inclusion and exclusion criteria. Influenza vaccine coverage among the elderly is high, though not as high as suggested by the official figures. Estimates on effectiveness are scarce. The majority come from ecological studies that show a modest reduction in mortality and hospital admissions due to influenza-related causes. Such reduction is not evident in the North and Northeastern states of Brazil, a finding that is probably related to the different seasonal pattern of influenza in equatorial and tropical regions. Brazilian epidemiologists still owe society better-designed studies addressing the effectiveness of influenza vaccine campaigns.

Estimating potential demand and supply of dengue vaccine in Brazil

Dengue is endemic in Brazil. Several dengue vaccine candidates, including one at the Butantan Institute in Sao Paulo, are being evaluated in clinical trials and may be licensed in several years. This study estimates the potential doses of dengue vaccine needed in Brazil under different scenarios in the first 5 years after vaccine introduction. Estimates were based on 2015-2022 country population projections. An estimated country population of 200-209 million with an annual 3.3-3.5 million cohort in the 12 to 23 month age group was included in the analysis. Computations were made for vaccines requiring one, two and three doses. A total of 7.8-62.9 million doses would be needed for only routine vaccination of 12-23 months cohort in first five years with different vaccination schedules. A combination of country-wide routine 12-23 month-old vaccination plus catch-up vaccination of individuals up to 40 years age is an appropriate strategy to control dengue. For this combination strategy, 129-425 million doses would be needed in the first five years after introduction. If vaccination is not provided to areas with low incidence of dengue, an estimated 108-360 million doses would be needed. This study provides a range of vaccine uptake estimates under different scenarios based on disease epidemiology. Actual demand and uptake will depend on the country vaccine introduction policy and strategies, vaccine supply capacity, cost, and vaccine profile. We consider one option based on the availability of vaccine from different sources. A more advanced vaccine uptake model based on estimates of vaccine impact under various scenarios should be developed.

The dilemma of influenza vaccine recommendations when applied to the tropics: the Brazilian case examined under alternative scenarios

Since 1999 the World Health Organization issues annually an additional influenza vaccine composition recommendation. This initiative aimed to extend to the Southern Hemisphere (SH) the benefits-previously enjoyed only by the Northern Hemisphere (NH)--of a vaccine recommendation issued as close as possible to the moment just before the onset of the influenza epidemic season. A short time between the issue of the recommendation and vaccine delivery is needed to maximize the chances of correct matching between putative circulating strains and one of the three strains present in the vaccine composition. Here we compare the effectiveness of the SH influenza vaccination adopted in Brazil with hypothetical alternative scenarios defined by different timings of vaccine delivery and/or composition. Scores were based on the temporal overlap between vaccine-induced protection and circulating strains. Viral data were obtained between 1999 and 2007 from constant surveillance and strain characterization in two Brazilian cities: Belém, located at the Equatorial region, and São Paulo, at the limit between the tropical and subtropical regions. Our results show that, among currently feasible options, the best strategy for Brazil would be to adopt the NH composition and timing, as in such case protection would increase from 30% to 65% (p<.01) if past data can be used as a prediction of the future. The influenza season starts in Brazil (and in the equator virtually ends) well before the SH winter, making the current delivery of the SH vaccination in April too late to be effective. Since Brazil encompasses a large area of the Southern Hemisphere, our results point to the possibility of these conclusions being similarly valid for other tropical regions.