Search

Background: The optimal vaccination is an essential public health strategy to control the pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This study aims to simulate the optimal vaccination strategy to control the virus epidemic by developing an age-specific model based on the transmission of coronavirus disease 2019 (COVID-19) in Wuhan City, China. Methods: An age-specific mathematical model based on the data of COVID-19 cases in Wuhan City from December 2, 2019 to March 16, 2020 was developed, with two scenarios for controlling transmission and reducing severity to estimate the effectiveness of SARS-CoV-2 vaccination strategy. Findings: Before the lockdown of the Wuhan City, the highest transmissibility of SARS-CoV-2 was among 14-44 years old (effective reproduction number, Reff = 4·28), followed by 14-44 to 45-64 years old (Reff = 2·61), and 14-44 to ≥ 65 years old (Reff = 1·69). We found that the first priority for controlling transmission should be to vaccinate nearly 90% individuals of 14-44 years old, followed by 90% individuals of 45-64 years old. However, the optimal vaccination strategy for reducing severity defined individuals ≥ 65 years old in vaccination priority groups, followed by 14-44 years old groups. Interpretation: The scenario analyses suggested that the optimal vaccination strategy aimed at controlling the transmission of COVID-19 might be to vaccinate about 90% of 15-44 years old individuals; while for reducing severity, the vaccination priority should focus on the older population. Furthermore, we also presented evidence about the heterogeneity of age-specific transmission and vaccination in different areas. Funding Statement: Bill & Melinda Gates Foundation, and the Science and Technology Program of Fujian Province. Declaration of Interests: The authors declare no competing interests.

In China, the malaria elimination program was launched in 2010 with the objective to eliminate this disease by 2020. Large-scale malaria control and elimination actions have been conducted with significant success since inception of the nationwide program. The incidence of locally acquired malaria has declined sharply along with the concomitant decrease of malaria-endemic areas from 762 counties reporting malaria in 2010 to just two counties adjacent to border areas (Yunnan, China-Myanmar and Tibet, China-India) in 2016. In total, 1723 counties (79%) and 134 prefectures (52%) had completed the malaria elimination internal assessment by the end of 2016. The year 2017 was the first year without report of indigenous malaria cases throughout the country. Hence, this chapter is meant to share the lessons learned from malaria elimination in China benefiting countries on the way to malaria elimination.

Background: Tengchong County was one of the counties located at the China-Myanmar border with high malaria incidence in the previous decades. As the pilot county for malaria elimination at the border area, Tengchong County is aiming to be the first county to achieve malaria elimination goal. A cross-sectional entomological survey was carried out to evaluate the feasibility of elimination approach and assess the receptivity of malaria reintroduction. Methods: Light traps associated with live baits were used to investigate the abundance of adult mosquitoes in nine villages in Tengchong County. Light traps were set to collect adult mosquitoes in both human houses and cowsheds from dusk till dawn in each site. Results: A total of 4948 adult Anopheles mosquitoes were collected from May to December in two villages. Of the mosquitoes were captured, 24.2% were in human houses and 75.8% in cowsheds. The peak of abundance occurred in July for An. sinensis and in September-October for An. minimus (s.l.) Ten Anopheles species were collected, the most prevalent being An. sinensis (50.3%), An. peditaeniatus (31.6%) and An. minimus (s.l.) (15.8%), contributing to 97.6% of the sample. Potential breeding sites were also investigated and a total of 407 larvae were collected, with An. sinensis (50.1%) and An. minimus (s.l.) (46.2%) as predominant species. Ponds and rice fields were the two preferred breeding sites for Anopheles mosquitoes; however, the difference between the number of adults and larvae captured suggest other breeding sites might exist Both An. sinensis and An. minimus (s.l.) were found zoophilic with human blood index as 0.21 and 0.26, respectively. No Plasmodium positive Anopheles specimens were found by PCR among 4,000 trapped mosquitoes. Conclusions: Although no indigenous malaria cases have been reported in Tengchong County since 2013, there is still a risk from the presence of vectors in the context of human population movements from neighboring malaria endemic areas. The presence of An. sinensis, associated to rice fields, is particularly worrying. Sustained entomological surveillance is strongly suggested even after malaria elimination certification.

China is approaching malaria elimination; however, well-documented information on malaria vectors is still missing, which could hinder the development of appropriate surveillance strategies and WHO certification. This review summarizes the nationwide distribution of malaria vectors, their bionomic characteristics, control measures, and related studies. After several years of effort, the area of distribution of the principal malaria vectors was reduced, in particular for Anopheles lesteri (synonym: An. anthropophagus) and Anopheles dirus s.I., which nearly disappeared from their former endemic regions. Anopheles sinensis is becoming the predominant species in southwestern China. The bionomic characteristics of these species have changed, and resistance to insecticides was reported. There is a need to update surveillance tools and investigate the role of secondary vectors in malaria transmission.