Sustainable Development Goals proposed by WHO, which aimed to achieve universal health coverage, including access to safe, effective and quality essential vaccines for all[5]. The supply of vaccines was essential to achieving universal health coverage. WHO had paid more attention to vaccine shortage in the report of addressing global drug and vaccine shortages[6]. Technical definitions of vaccine shortages should be developed as needed and the analysis should be from the supply side and the demand side. This study also analyzed the supply and demand of vaccine for childhood immunization programs in China. The results showed that the supply and demand of vaccine for childhood immunization programs in China were roughly balanced as a whole from 2016 to 2019, but there was a potential shortage of some vaccines in each year, and the number of vaccine with potential shortages increased.
In recent years, vaccine-related events occurred frequently in China. In 2017 and 2018, the number of batches of DPT vaccine was reduced due to disqualification of DTP vaccine potency produced by Wuhan Institute of Biological Products Co., Ltd and "Changchun Changsheng" Vaccine event in 2018, and there is a risk of shortage of DPT vaccine in 2017 and 2018.In addition, due to the impact of the "Changchun Changsheng" vaccine event in 2018, all live L-HepA produced by Changchun Changsheng Enterprise were not allowed to use and the company had stopped production, and as a result of this, the supply and demand ratio of hepatitis A vaccines in 2018 was only 65.63%, and there is a risk of shortage. The shortage of vaccine is a worldwide problem[7–10], and both UK and the United States have faced shortages[11] [12–14].
After the Changchun Changsheng Vaccine Incident in 2018, China issued the vaccine management law of the People's Republic of China, which tightened the supervision of the entire vaccine chain and further reduced the number of vaccine batches issued in 2019. Five kinds of vaccines could be in short supply in 2019. During 2016 to 2019, both DT and MPSV-A vaccines are only produced by Wuhan Institute of Biological Products Co., Ltd and the price of these vaccines was lower than other vaccines without shortage. All of these factors contributed to the vaccine shortage. Temporary yellow fever vaccine shortages had occurred in the United States as a result of manufacturing problems, at that time only one yellow fever vaccine was licensed for use in the United States[15].
In 2016, China carried out the program conversion of polio vaccine, TOPV (sugar pill) was no longer used, and IPV and BOPV were used for vaccination. However, IPV is only produced by one manufacturer (Institute of Medical Biology, Chinese Academy of Medical Sciences), with limited production capacity and only 3.45 billion batches issued. To further boost supply, the vaccines made Sanofi by were purchased to increase supply, but only 7.28 million batches were issued by Sanofi. The batch issued by the two companies still cannot meet the demand, and there may be a shortage of polio vaccine in 2016. Many countries will face shortages of the IPV vaccine and 28% of countries (35 of 125) still had not been able to introduce IPV because of supply constraints or experienced a stock-out of vaccine according to WHO [16].
Vaccine is a national strategic and public welfare product, and the availability of vaccine reflects the fairness of society. Maintaining a balance between supply and demand for vaccines is therefore critical to preventing unfair events and the risk of epidemics arising from vaccine shortages. However, the analysis of vaccine supply and demand is complicated and affected by many factors, and this study also has some limitations: this study only analyzes the relationship between supply and demand from the perspective of the whole country, and does not analyze the situation of each provinces. There may be local shortages and surpluses caused by the unbalanced distribution of vaccines in some regions[17]
In conclusion, the supply of vaccines in China's national immunization program can meet the
demand of vaccines, but some vaccines are at risk of shortage. Reasons for these possible shortages were multi-factorial and included companies leaving the vaccine market, manufacturing or production problems, and Changes in vaccine procedures for immunization programmes[18, 19]. In 2020, China had faced with the serious threat of novel coronavirus epidemic, and the production and distribution of vaccines will be affected by the shutdown. Therefore, it is necessary for the country to develop a vaccine reserve mechanism in the next step, so as to avoid the shortage of vaccine supply in the childhood immunization program and prevent the timely and effective supply of vaccine from the impact of major public health emergencies[20].However, the decision to establish and maintain a vaccine stockpile is complex and must take the consideration of disease burden[21], stockpile sizes, funding, the number of manufacturers, unanticipated production problems, and the dynamic nature of the vaccine market.