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This open-label, randomized, phase 3 study in China (V260-074; NCT04481191) evaluated the immunogenicity and safety of concomitant and staggered administration of three doses of an oral, live, pentavalent rotavirus vaccine (RV5) and three doses of an intramuscular, inactivated poliomyelitis vaccine (IPV) in 400 healthy infants. The primary objective was the non-inferiority of neutralizing antibody (nAb) responses in the concomitant- versus the staggered-use groups. Antibody responses were measured at baseline and 1-month post-dose 3 (PD3). Parents/legal guardians recorded adverse events for 30 or 15 d after study vaccinations in the concomitant-use or staggered-use groups, respectively. At PD3, >98% of participants seroconverted to all three poliovirus types, and the primary objective was met as lower bounds of the two-sided 95% CI for between-group difference in nAb seroconversion percentages ranged from - 4.3% to - 1.6%, for all poliovirus types, p  < .001. At PD3, geometric mean titers (GMTs) of nAb responses to poliovirus types 1, 2, and 3 in the concomitant-use group and the staggered-use group were comparable; 100% of participants had nAb titers ≥1:8 and ≥1:64 for all poliovirus types. Anti-rotavirus serotype-specific IgA GMTs and participants with ≥3-fold rise in postvaccination titers from baseline were comparable between groups. Administration of RV5 and IPV was well tolerated with comparable safety profiles in both groups. The immunogenicity of IPV in the concomitant-use group was non-inferior to the staggered-use group and RV5 was immunogenic in both groups. No safety concerns were identified. These data support the concomitant use of RV5 and IPV in healthy Chinese infants.

Background: There has been no data on the immunogenicity and safety of the 4 th booster dose of the sIPV immunization in 18-24 months old children in post-marketing studies of large cohort providing with robust results., Method: In a phase Ⅳ randomized, double-blinded clinical trial, 1200 participants aged 2 months were immunized with three consecutive doses of sIPV at 2, 3, and 4 months old to complete primary immunization. Out of the 1200 participants, 1129 received the 4 th dose of sIPV as booster immunization. Immunogenicity was evaluated in 1100 participants., Results: Seropositive rates of the anti-poliovirus type 1, 2, and 3 neutralizing antibodies were 99.9 %, 98.0 %, 98.2 %, respectively, with GMTs of 557.0, 146.1, 362.0 one year after primary vaccination. After booster vaccination between 18 and 24 months old, the seropositive rates for 3 types all reached 100.0 %, with GMTs of 8343.6, 5039.6, 5492.0, respectively. Particularly for the anti-poliovirus type 2 antibody, the GMT was 230.4 after primary immunization, maintained to 146.1 one year after primary immunization, and increased to as high as 5039.6 after booster vaccination. The GMT ratios between each batch groups after booster immunization were between 0.67 and 1.50, meeting the immunological equivalence criteria. The incidence rate of adverse reaction was 23.0 %, which was comparable to those in the phase Ⅲ trial but had a lower incidence. Furthermore, no SUSAR was reported in this study., Interpretation: In conclusion, as the anti-poliovirus antibodies gradually waned one year post sIPV primary vaccination, especially the type 2 antibody waned to a very low level, suggesting the importance of the booster immunization for children at the age of 18-24 months old. The booster shot can greatly enhance the antibody level and protect children from the potential risk of infection with WPV and VDPV by supplementing the anti-poliovirus type 2 immunity gap in the current real world. Clinic Trial Registration. NCT04224519., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Introduction: Several vaccine events causing public concern have occurred in China that were investigated and responded to by the central government. We describe causes, influences, and policy or practice changes associated with vaccine events that occurred between 2005 and 2021. We make recommendations to foster resilience in China's Expanded Program of Immunization (EPI) system and vaccination enterprises and to sustain vaccine and program confidence., Methods: Our study included all vaccine events since 2005 that were investigated and responded to by the central government of China. We verified mainstream and social media visibility of the events through Internet search. We extracted event times, causes, investigation processes, results, actions, and policy or practice regulation changes from official reports of government meetings and from official websites with media briefings., Results: Seven vaccine events were identified, each of which caused more than 100,000 mainstream or social media reports nationally or nationally and internationally. The events ranged in magnitude from 145 children receiving out-of-date oral poliovirus vaccine to a measles supplementary immunization activity involving 103 million children. Few, if any, children were directly harmed by vaccines in the events. Government responded to each event with program or policy changes, and in one case, with legislation. Responses affected the conduct of campaigns and supplementary immunization activities, use of schools as vaccination venues, financial incentives for vaccinating with non-program vaccines, vaccine procurement and distribution, and program policy making. The most fundamental response was enacting the country's first vaccine law, the 2019 Vaccine Administration Law, which guides virtually all aspects of vaccination work, from vaccine development through regulation, program implementation, and safety and impact monitoring., Conclusions: All seven events generated substantial national and international mainstream and social media criticism and discussion, most commonly expressed through concerns of vaccine safety or vaccine effectiveness. Most had temporally associated temporary declines in vaccine confidence and coverage, jeopardizing decades of vaccination effort. The central government responded to each event by attempting to address root causes. Faithful implementation of the Vaccine Administration Law is fundamental to program strengthening and sustaining confidence of families, stakeholders, and government in vaccines and immunization in China., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Since the Global Polio Eradication Initiative was launched by the World Health Assembly in 1988, significant progress has been made in global polio prevention and control. But the occurrence of vaccine-associated paralytic poliomyelitis cases and vaccine-derived poliovirus related cases have become a major challenge during the post-polio era. While coronavirus disease 2019(COVID-19) has brought serious disease burden and economic burden to all countries in the world, prevention and control of vaccine-preventable infectious diseases such as polio should not be neglected under the background of the global common fight against COVID-19. Taking the type Ⅲ VDPV cycle event in Shanghai as an example, the paper discussed how to do a good job of routine inoculation under the prevention and control of COVID-19 to strictly prevent the outbreak of vaccine-preventable infectious diseases.

The switch from using only trivalent oral polio vaccine (tOPV) to sequential schedules combining inactivated poliovirus vaccine (IPV) and bivalent oral polio vaccine (bOPV) for polio vaccination will cause changes to mucosal immunity against polio in infants, which plays an important role in preventing the poliovirus spread. Here, we analyzed mucosal immunity against poliovirus in the intestine during different sequential vaccination schedules. We conducted clinical trials in Guangxi Province, China on 1,200 2-month-old infants who were randomly assigned to one of three vaccination schedule groups: IPV-bOPV-bOPV, IPV-IPV-tOPV, and IPV-IPV-bOPV, with vaccine doses administered at 8, 12, and 16 weeks of age. Stool samples were collected from 10% of participants in each group before administration of the second vaccine doses and at 1, 2, and 4 weeks after the administrations of the second and third vaccine doses. Immunoglobulin A (IgA) in the stool samples was measured to analyze the mucosal immune response in the intestine. Because of the absence of poliovirus type 2 in bOPV, the vaccination schedule of IPV-IPV-bOPV did not sufficiently raise intestinal mucosal immunity against poliovirus type 2, although some cross-immunity was seen. The level of intestinal mucosal immunity was related to shedding status; shedders could produce intestinal mucosa IgA more quickly. The intestinal mucosal immunity level was not related to serum neutralizing antibody level. In the combined sequential vaccination schedule of IPV and bOPV, the risk of circulating vaccine-derived poliovirus type 2 (cVDPV2) may be increased owing to insufficient intestinal mucosal immunity against poliovirus type 2.

One dose of inactivated poliovirus vaccine (IPV) was introduced into the Chinese Expanded Program on Immunization (EPI) in 2016. IPV made from Sabin strains (sIPV) was newly licensed in China and its safety has been concerned. This study aimed to evaluate the safety of sIPV and provide a comparison with conventional IPV made from wild strains (wIPV). We collected all IPV-related AEFI reports in Jiangsu from the Chinese National Adverse Events Following Immunization Information System (CNAEFIS) for 2016-2019. We obtained the administered doses of IPV from the Jiangsu provincial Electronic Immunization Registries System (JSEIRS). The AEFI reporting rates per 100,000 doses of vaccine administered were compared for sIPV and wIPV. A total of 699 sIPV and 908 wIPV AEFI cases were collected by CNAEFIS in Jiangsu during 2016-2019. The overall AEFI reporting rates were 53.02 per 100,000 doses and 41.25 per 100,000 doses for sIPV and wIPV, respectively ( P < .001). For both sIPV and wIPV, the AEFIs were mainly classified as common adverse reactions. The reporting rate of common adverse reactions was higher for sIPV than for wIPV ( P < .001). The most frequently reported symptoms/signs were fever, persistent crying, injection site erythema/swelling, rash, and injection site induration. Only 1.14% of sIPV-associated and 2.31% of wIPV-associated AEFI cases were diagnosed as serious. No difference in reporting rate was observed for serious AEFIs ( P = .272). sIPV has a favorable safety profile, although it exhibits a slightly higher reporting rate of common adverse reactions than wIPV.

A new vaccination schedule with one dose of inactivated polio vaccine (IPV) followed by three doses of bivalent oral attenuated live polio vaccine (bOPV) was introduced in China in 2016. Both Sabin IPV (sIPV) and Salk IPV (wIPV) sequentially with bOPV were accepted in the Chinese routine vaccination schedule. We intended to assess the immunogenicity of the current primary schedule (s/wIPV-bOPV-bOPV) and the schedule in the early stage of the switch (tOPV-bOPV-bOPV), and compare immunogenicity between the groups with different polio virus strains. Healthy infants aged 60-89 days were recruited in hospitals in Chongqing. Infants were assigned to one of three treatments (tOPV-bOPV-bOPV, sIPV-bOPV-bOPV or wIPV-bOPV-bOPV) by enrollment time. Polio neutralizing antibody (NA) assays were conducted to assess immunity. 1027 eligible infants were enrolled. Over 95% seroprotection rates against type I poliovirus (PV1) and type III poliovirus (PV3) were observed in all groups. Infants who received tOPV-bOPV-bOPV had higher antibody titers against type II poliovirus (PV2) than did the IPV-bOPV-bOPV. The geometric mean titers (GMTs) of PV2 were only ~20 in the IPV-bOPV-bOPV. GMTs of PV1 were higher than PV3 in s/wIPV-bOPV-bOPV. The primary schedule of s/wIPV-bOPV-bOPV is insufficient to protect children against PV2, and the NA titer to PV3 is lower. Higher antibody responses were induced in sIPV-bOPV-bOPV than that in wIPV-bOPV-bOPV. Supplementary vaccination with one dose of IPV is necessary for children who had no tOPV immune history or had only one IPV to induce higher levels of immunity against PV2 and PV3.

Background: A domestic Sabin strain-based inactivated poliovirus vaccine (Sabin IPV) was approved by China Food and Drug Administration in 2017 as a replacement for the Salk strain-based inactivated poliovirus vaccine (Salk IPV) that has been in use in China for over 10 years. The present post-marketing trial was implemented in China to assess the immunogenicity and safety of replacing the Salk IPV with the Sabin IPV in the last two immunizations of the standard three-dose schedule., Methods: We conducted a randomized, controlled clinical trial with two groups that received three doses of IPVs at the age of 2, 3, and 4 months: the Salk-Sabin-Sabin group and the Salk-Salk-Salk group. Blood samples were collected before vaccination and 30-40 days after the third dose of vaccination. The seroconversion rates and antibody geometric mean titers (GMTs) were calculated and analyzed to evaluate immunogenicity. The safety of both immunization schedules was also monitored and analyzed., Results: Of 360 recruited healthy infants, all three IPV doses were administered and blood collection was completed in 330 infants. All participants (100%) in both groups were seropositive for all three poliovirus types after the last vaccination. There were significant differences between the two groups (P < 0.001) in the GMTs for antibodies against poliovirus types 1 and 2, but no significant difference was observed for antibodies against type 3 (P = 0.009). A non-inferiority t-test showed that the post-immunization GMTs for all three types in the Salk-Sabin-Sabin group were not inferior to those in the Salk-Salk-Salk group (P < 0.001). Safety assessment indicated that there was no significant difference in the incidence of all adverse events between the two groups (P = 0.806)., Conclusions: The Salk-Sabin-Sabin IPV immunization schedule is not inferior to the Salk-Salk-Salk IPV schedule in terms of both immunogenicity and safety. Clinical trial number: NCT04051736., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In 2000, China was declared polio-free. However, in 2018, wild poliovirus (WPV) was still endemic in two of its neighboring countries, making WPV importation and outbreak alarming possibilities. This study documents the seroprevalence of poliovirus antibodies before and after the polio vaccine switch in 2012 and 2017 in Beijing. Cross-sectional population-based serologic surveys were conducted in 2012 and 2017 in Beijing. The study subjects were selected from 10 different age groups (<1, 1-4, 5-9, 10-14, 15-19, 20-24, 25-29, 30-34, 35-39, and ≥40 y) using a multi-stage-stratified sampling method. Neutralizing antibody titers against poliovirus serotypes 1 (P1), 2 (P2), and 3 (P3) were assayed by World Health Organization standards. The seropositive rates (SR) and geometric mean titer (GMT) of the neutralizing antibodies were 91.71% and 1:130.26, respectively, for P1, 94.09% and 1:113.39, respectively, for P2, and 88.78% and 1:79.65, respectively, for P3 before the switch in 2012, and 87.78% and 1:108.93, respectively, for P1, and 81.67% and 1:70.56, respectively, for P3 after the switch in 2017, with a statistically significant difference for P1 and P3 between 2012 and 2017. The neutralizing antibodies for all poliovirus serotypes differed among different age and vaccination groups in both 2012 and 2017. After switching polio vaccines twice in 2014 and 2016, the P1 and P3 polio antibody levels were lower in 2017 than in 2012. The P2 antibody levels were determined from the first dose of IPV. The seroprevalence of poliovirus antibodies after adjustment of the immunization schedule of the polio vaccine on January 1, 2020, must be further monitored.

Background: An outbreak of an imported Type 1 wild poliovirus from Pakistan occurred in the Xinjiang Uygur Autonomous Region of China in 2011, although the local immunity status of the oral polio vaccine (OPV) was relatively satisfied., Methods: Neutralizing antibody titers against the Xinjiang strain and Sabin 1 strain were measured in 237 sera from 3 groups of fully OPV-vaccinated persons and 1 group of infants fully vaccinated with the inactive polio vaccine (IPV). Additionally, 17 sera collected from 1 Xinjiang poliomyelitis case and his 16 contacts were also tested. Genomic sequencing was conducted the Xinjiang strain., Results: The antibody titers against the Xinjiang strain in each of 237 sera were significantly lower than those against the Sabin 1 strain. Notably, 40.0% of children in Group 1 were seronegative against the Xinjiang strain, which indicated that they might play an important role in wild poliovirus transmission, although their antibody titers against the Sabin 1 strain varied between 1:8 and 1:512. Meanwhile, serological results of the Xinjiang poliomyelitis case and his contacts also provided evidence that a proportion of OPV-vaccinated children had indeed been involved in the transmission chain of the Xinjiang outbreak. Genomic sequencing indicated that the Xinjiang strain was greatly distinguishable from the Sabin 1 strain in neutralizing antigenic sites., Conclusion: The lack of neutralizing antibodies against the Xinjiang strain in persons vaccinated by OPV may be associated with the transmission of Type 1 wild poliovirus in Xinjiang. Using Salk IPV along with OPV might be considered in a wild poliovirus outbreak response, especially in the countries which continued to have persistent wild poliovirus circulation., (© The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Objective: Study on the epidemiological characteristics of poliomyelitis virus in Yunnan, from 2003 to 2007., Methods: Surveillance data of acute flaccid paralysis (AFP) cases from year 2003 to 2007 was gathered. All the stool specimens were identified to contain polio virus., Results: 1171 AFP cases were reported. Out of the total number of 1138 stool specimens from 2003 to 2007, 57 cases showed polio virus (5.0%), 159 showed NPEV (14.0%), 922 cases showed virus negative. In those virus, polio type II took the lead (31.6%). 57 AFP cases appeared in 37 (28.7%) counties in Yunnan. Most of the cases were under 2 years of age. 29 cases had taken more than 3 OPV (oral poliovaccine) dosages and 41 cases had fever before paralysis occurred. Most of the cases appeared paralysis on single lower limb, but 26 cases leaving deformity. Significant difference was found between the two groups: having received vaccination more than 3 OPV dosages or less than 3 dosages., Conclusion: High quality AFP epidemiological and laboratory surveillance program, together with OPV routine and supplemental immunization strategy to cover the poorly immunized area/population appeared to be most effective.

Objective: Hainan Province was a hyperendemic area of poliomyelitis, with an average incidence rate of 0.28 per hundred thousand before 1993. A series of strategy was developed for polio eradication in the whole province in July 1993., Methods: Health education, regular and strenthening immunization programs, AFP surveillance., Results: 1. OPV vaccination rate increased to 97.93%, 2. incidence rate of polio had a 80.93% reduction, 3. seasonal peak of epidemic was cut down, 4. endemic cycle was broken and 5. the endemic area became smaller. The number of counties (cities) where polio cases occured reduced for 81.33% in 1993 than that in 1989. Four boosters had been implemented from 1993 to 1997, to eliminated blank spots of immunization. The average geometric antibody of titre increased to 1:400 and above. After the establishment of polio surveillance system in 1991, 1. the reporting rate of non-AFP increased from 0 to 1.27 per hundred thousand, 2. rate of double specimens collection increased from 0 to 87.10%, 3. positive rate of virus isolation from 23.07% to 34.80%, 4. the positive specimens were appraised by National Polio Surveillance Center and no wild strain was found. Health education has made remarkable impact and immunization knowledge among parents had a 75 percentage point increase., Conclusion: Results showed that strategy of polio eradication has made positive effects and provided valuable experiences for the control or elimination of diseases which can be prevented by vaccines.

It is difficult to conduct the epidemiological survey with accurate statistical theory in the developing countries due to the problems especially emerged in the developing countries such as no availability of the accurate population data, limitation of the time for survey, geographical obstacle and financial problems. In the consideration of the health needs in those countries, results of the epidemiological survey should be reflected in the present health projects as rapidly as possible. The authors conducted the survey for the immunization coverage of oral poliomyelitis vaccine(OPV) in China by the questionnaire and interview. The data was analyzed by using the Hayashi's quantification theory type 2 and made clear about the relationship between the health behaviors for immunization among residents and several factors. It is considered that this theorem can provide the obvious numeral materials about multi-factorial cause effect relationship for the decision making and is useful for the rapid assessment or initial survey in the developing countries.

In order to reveal immunization status of children in migrating families and its related risk factors, a study was conducted in Beijing, Inner Mongolia and Fujian from August to November, 1996. Results showed that the overall coverage with BCG, OPV, DPT and MV was 34.26% (95% CI: 29.75%-38.94%). Many factors influenced the immunization status of floating children which mainly consisted of a) regular searching for new coming floating children conducted by EPI staff, b) awareness of parents on the number of the total EPI-targeted vaccines, c) home as the place that the child was born, d) the length did the child's mother stay at the place, e) how well did the parents comply to the vaccination and f) The type of hospital was chosen when seeing a doctor.

A large nationwide outbreak occurred in 1989-1990 in China, in which nearly 10,000 poliomyelitis cases were reported. After two rounds of oral poliovirus vaccine (OPV) supplemental activity in nearly every province in the 1992-1993 winter season, no wild poliovirus was detected in 1993 in 22 provinces in the middle of China that contained 86% of the population. During the first national immunization days (NIDs) conducted in December 1993 and January 1994, 83 million children 0-47 months of age were immunized. In 1994, wild poliovirus was identified in only 6 of 2397 children with stool specimens tested. After a second NID in December 1994 and January 1995, no wild poliovirus was detected in 1995 despite a very high level of virus surveillance. In summary, double-round mass supplemental OPV immunizations in children 0-3 years old in two consecutive winters eliminated wild poliovirus from 23% of the world's population (1.2 billion people).

The World Health Organization recommends conducting supplemental immunization activities to eradicate poliomyelitis by the year 2000. Although effective in eliminating poliomyelitis from the Americas, supplemental campaigns require substantial resources. To assess differential campaign effectiveness in eliminating this disease, poliomyelitis occurrence was compared in counties in China that targeted children <3 versus <4 years of age. Counties that targeted children <3 years of age reported poliomyelitis more frequently after the campaigns. This association was observed even after accounting for the effects of previous poliomyelitis occurrence, urban versus rural setting, and population density. While several limitations emphasize the preliminary nature of these findings, these data support targeting the widest possible age group of susceptible children to ensure maximum effectiveness in eliminating poliomyelitis. Thus, while reducing the target age of these activities may result in considerable resource savings, such campaigns may not be as effective in eliminating poliomyelitis.

In 1994, the number of reported polio cases was 307 in China. This number was 53% lower than that in 1993, and was the lowest record ever in China. In 1994, the distribution of polio cases was highly dispersed and the number of outbreak was reduced obviously. Of 225 counties which reported polio cases in 1994, polio outbreak occured in 2 counties. Cases due to polio outbreak accounted for 4.2% of the total cases. The distribution of polio wild virus was narrow but the regional difference still existed. In the southeast, high risk region for polio consisting Guangdong, Hainan, Fujian three provinces, the number of polio cases decreased remarkably in 1994. On the contrary, in the southwest region which, consisting Guangxi, Yunnan, Guizhou, Sichuan four provinces, the number of polio cases increased obviously, accounted for approximately a half of the total number in 1994. During the coming 1 to 2 years, we should emphasis on these regions and provinces where high incidence was noticed in our polio eradication program. Those provinces should include Xinjiang, Fujian. Hubei three provinces that polio wild virus was identified in 1994, and Guangxi, Sichuan, Guizhou, Yunnan in the south west region as well. We should further increase Polio vaccination coverage of children especially floating and unplanned ones through strengthening routine immunization and carring out new national immunization day activity.

After a series of poliomyelitis outbreaks came about in Shandong province from 1988 to 1990, comprehensive measures including establishment of acute flaccid paralysis (AFP) surveillance system, introduction of mass immunization campaign of oral poliovirus vaccine (OPV) and enhancing management of poliomyelitis eradication activity, were carried out. The incidence of poliomyelitis decreased with the reported number of cases 95, 25, 22 and 17, in 1991, 1992, 1993 and 1994, respectively. A geographically sporadic distribution was noticed with no peak on seasonality. No confirmed case caused by wild poliovirus was identified from 1991 to 1994. Reporting incidence of AFP cases among children under 15 years old was increasing gradually with 1.00 per 10(5) population in 1993 and 1.89 in 1994. The results showed that the poliomyelitis eradication activity in Shandong province had reached a final stage but much efforts still need to be made to reach the target on poliomyelitis eradication.

In Shandong Province, China, programmes were initiated in 1991 for mass immunization against poliomyelitis and for the immediate reporting of acute flaccid paralysis (AFP). The incidence of non-poliomyelitis AFP was found to be 0.46-0.61 cases per 100,000 children per annum. It appeared that illness resembling the Guillain-Barré syndrome was underreported. The incidence of such illness peaked among children aged 2-3 years. Although laboratory investigations have improved, in 1992 they were still inadequate in nearly a third of confirmed poliomyelitis cases. As the prevalence of wild poliovirus declines in China, reliable laboratory support needs to be established and adequately sensitive and specific AFP surveillance be developed if poliomyelitis is to be eradicated.

In 1988, the World Health Organization (WHO) established the goal of global eradication of poliomyelitis by the year 2000. Based on cases officially reported to WHO, progress toward eradication has been substantial: in 1992, a total of 15,445 paralytic poliomyelitis cases were reported worldwide, compared with 32,419 cases in 1988. Beginning in December 1993, the People's Republic of China will conduct a series of two National Immunization Days that target approximately 100 million children (all children aged < 4 years) to receive oral poliovirus vaccine (OPV) in each of two separate rounds of vaccination, possibly representing the largest public health event of its kind in history. This report summarizes the plans for National Immunization Days and efforts in China to eradicate poliomyelitis by 1995.

In 1989, there was a poliomyelitis outbreak in Pi county, Jiangsu province. The total case number was 597 in which 52 died. It caused the patients' families and national economic loss 2,713,107.32 yuan and lessened creating value of 18,583,942.35 yuan for the country. The outbreak was mainly caused by the fact that many children did not set vaccination card, missed vaccination chance and lacked in immunity to polio. So the ratio of cost-benefit will be expected to reach 1:6.85, and the net benefit of 2,317,268.16 yuan can be gained if the task of EPI is implemented well to avoid the occurrence of outbreak.

The survey was conducted in four counties where Polio consistently occurred during 1986-1988. According to the survey, there were 251 polio cases from 1974 to 1989, of which only 138 cases were reported. The paralytic rate by polio in the population under 15 years old was 0.486%. The survey also showed that polio was still a severe disease which paralysed children in the country. The number of polio cases accounted for 48% of all paralytic persons. Legs were the chiefly affected limbs, being about 90%. From analysis of vaccine history of polio cases, we found that the difference between two groups was highly significant. 90% of polio cases had no vaccine history or no full vaccine history. The reason for this was mainly due to lack of related knowledge. In addition, we also analysed multiple birth factor, which seemed to be not significant.

In Oct. 1989 we carried on the case-control study on children with polio in a few years, matched with 1:1 in two districts in Shandong province. According to the results of data of 117 pairs condition logistic stepwise regression was analysed. The major risk factors on polio are: no oral poliovaccine, distance between the place of vaccination and the house hygiene knowledge, type of drinking and annual revenue of the family. It was showed in order to prevent polio, we must strengthen propaganda on hygiene knowledge and improve hygiene environment when enhancing oral polio vaccine rate increasingly.