Journal of Vaccine Research 2024, Vol.14, No.1, 17-26 http://medscipublisher.com/index.php/jvr 19 Simultaneously, American researcher Albert Sabin was also dedicated to polio vaccine research. Sabin's focus was on developing an oral live attenuated vaccine. Through studying the biological characteristics and replication process of the virus, he successfully created an oral live attenuated polio vaccine. This vaccine was not only safe and easy to administer but also capable of eliciting long-lasting immune responses, effectively preventing poliomyelitis. Under the efforts of Salk and Sabin, both the inactivated and oral live attenuated polio vaccines underwent continuous improvement and refinement. In the 1950s and 1960s, these two vaccines were subjected to large-scale clinical trials and promotion worldwide. The trial results showed that both vaccines were highly safe and effective in preventing poliomyelitis transmission. 1.3 Promotion and widespread use of vaccines Since the successful development of polio vaccines, there have been extensive efforts to promote and ensure the widespread use of these vaccines worldwide. Various measures have been taken by the World Health Organization (WHO) and other international organizations regarding vaccine production and supply. For example, they collaborate with pharmaceutical companies to promote vaccine production and supply to ensure an adequate vaccine supply. Furthermore, they cooperate with governments of different countries to strengthen the regulation and control of polio vaccines, preventing counterfeit and substandard vaccines from entering the market. Regarding vaccine coverage, governments and public health organizations have also implemented various measures. For instance, in some impoverished regions and developing countries, governments and organizations organize special vaccination campaigns to provide free vaccination services for children. Additionally, they use various media channels to educate the public on the importance and safety of polio vaccines, as well as how to administer vaccines correctly. As a result of these efforts, the global vaccine coverage for polio has significantly improved. According to data from the World Health Organization, the number of polio cases has decreased by over 99% since 2000, primarily due to the promotion and widespread use of vaccines. However, despite significant progress in the promotion and widespread use of polio vaccines, challenges and difficulties still exist. For example, in some conflict-ridden, impoverished, and disaster-stricken areas, limitations in healthcare resources and infrastructure continue to pose difficulties in vaccine administration. Additionally, some members of the public, especially on social media, harbor doubts and misconceptions about vaccine safety, which can affect vaccine coverage. The promotion and widespread use of polio vaccines are a global collaborative process that requires the collective efforts of all parties. By strengthening vaccine production and supply, improving vaccine coverage, and enhancing public awareness and education, it is believed that China can better prevent and control the occurrence and transmission of poliomyelitis, making a greater contribution to the health and well-being of the global population (Orenstein and Ahmed, 2017). 2 Classification and Characteristics of Polio Vaccines 2.1 Live attenuated and inactivated vaccines Live attenuated vaccines are vaccines containing live viruses that have been altered or weakened to reduce their virulence. These vaccines can stimulate long-term immune responses in the human body, providing prolonged protection. Generally, live attenuated vaccines need to be stored in a refrigerator to ensure their viability. The advantage of live attenuated vaccines is that they can generate relatively long-lasting immune responses, but they also come with higher risks and potential side effects. Therefore, live attenuated vaccines are contraindicated for certain populations, such as individuals with weakened immune systems (Figure 2). Inactivated vaccines are a type of vaccine that contains viruses or pathogens that have been inactivated or killed during the preparation process. In the production of inactivated vaccines, the viruses are rendered nonfunctional through the use of chemicals or other methods to ensure that they cannot cause the disease. Inactivated vaccines are a safer choice for individuals with a weaker immune system. However, the duration of immunity provided by inactivated vaccines is relatively shorter, requiring periodic vaccinations to maintain their effectiveness (Figure 3).
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