一类疫苗是政府扩大免疫规划使用的疫苗，使儿童能预防12种传染病。一类疫苗免费向中国儿童提供，也是儿童必须接种的疫苗。二类疫苗是父母自主选择为儿童补充接种的疫苗，例如可预防B型流感嗜血杆菌所致疾病、侵袭性肺炎链球菌病和轮状病毒胃肠炎。接种二类疫苗需自费。
2.疫苗质量问题如何保证？
世卫组织对中国疫苗（包括一类疫苗和二类疫苗）的生产和许可有信心。中国管理疫苗的国家监管部门（国家食品药品监督管理总局和国家卫生和计划生育委员会）已于2010年和2014年通过世卫组织的评估，符合所有国际监管标准，包括能确保使用现行的药品生产质量管理规范（GMP）。此次疫苗事件主要与疫苗的储存和分发有关。一类疫苗由政府的疾控中心系统从生产商分发到接种点，其可控温度的冷链系统已通过世卫组织和联合国儿童基金会评估并确认为高质量的冷链系统。但是二类疫苗不通过该系统配送。
3.“无毒性反应”是否代表无害？
“无毒性反应”指儿童接种过期或储存不当的疫苗后生病的可能性极低。但是，如果疫苗由于过期或不当处理失去效力，儿童将缺乏疫苗针对疾病的预防能力，可能在未来感染疾病，对其造成伤害。这种情况跟未接种疫苗的后果类似。
4.若孩子接种了无效疫苗，要补种吗？
一般情况下，接种过期或不当处理的疫苗后，人体对疫苗针对的疾病可能不产生免疫能力，因此应该重新接种疫苗。重新接种疫苗是安全的，可以立即接种灭活疫苗，也可以在28天后接种减毒活疫苗。但是，由于不同疫苗可预防疾病在不同年龄阶段所产生的风险不同，所以不是所有疫苗都有必要重新接种。诸如麻疹、风疹、甲肝、乙肝和水痘等疾病，可通过血液检测了解儿童的免疫情况和确认是否需要重新接种疫苗。若考虑重新接种疫苗，应咨询预防接种点的专业人员。
5.安全风险非常低到底有多低？
据我们所知，未在规定温度范围内储存的疫苗或者过期疫苗不是被污染的疫苗或有毒性的疫苗。然而，问题在于不确定疫苗是否仍有效力。所有疫苗的接种均有一定的产生副作用的风险，例如对某疫苗成分出现过敏反应。但是，接种过期或不当储存的疫苗应当不会产生任何额外的副作用和毒性反应风险。
6.若孩子接种了无效疫苗，有何后果？
儿童在接种不当储存疫苗后，由于接种疫苗而生病的可能性极低。但是，若疫苗由于过期或不当处理失去效力，该儿童将缺乏疫苗针对疾病的预防能力，可能在未来感染疾病，对其造成伤害。这种情况跟未接种疫苗的后果类似。
7.应该给孩子注射疫苗吗？
是。中国儿童与全球其他儿童一样，需要疫苗的保护，避免感染疫苗可预防疾病。中国免疫规划可保护儿童免于患12种传染性疾病。除极少数儿童因医学原因无法接种疫苗之外，所有的儿童都应该根据常规免疫程序接种疫苗。接种疫苗是保护儿童避免感染疫苗可预防疾病的最安全途径。
WHO responds to questions raised regarding the vaccine report in China
Q1: What’s the difference between Category 1 and 2 vaccines in China?
Category 1 vaccines are vaccines in the government’s Expanded Program on Immunization that are used to protect children from 12 infectious diseases. Category 1 vaccines are provided free for all children in China, and it is mandatory in China for children to be vaccinated with these vaccines. Category 2 vaccines are additional vaccines that parents may choose to have for their children – and help protect against diseases such as Haemophilus influenza type b disease, invasive pneumococcal disease, and rotavirus gastroenteritis. Category 2 vaccines are not provided for free in China.
Q2: Who makes sure that Category 1 and Category 2 vaccines are safe?
WHO has confidence in the manufacturing and licensing of vaccines in China – both for Category 1 and Category 2 vaccines. The China National Regulatory Authorities for vaccines (CFDA and NHFPC) have been assessed in 2010 and 2014 by WHO and found to meet all international regulatory standards, including assuring use of current Good Manufacturing Practices. The issue in the current situation relates to storage and distribution of vaccines. Category 1 vaccines are distributed through the government’s CDC system, from manufacturer to clinic. This Controlled Temperature Chain has been evaluated by WHO and UNICEF and found to be of high quality. However, Category 2 vaccines are not distributed through the same system.
Q3: Does ‘no toxic reaction’ mean no harm?
“No toxic reaction” means that the child is extremely unlikely to get sick as a result of receiving the expired or improperly stored vaccine. However, if the vaccine had lost potency due to expiration or improper handling, the child could be harmed if he or she gets infected later in life because the impotent vaccine provided no protection from the disease for which the vaccine was intended. This situation would be the same as if the child had never received the vaccine.
Q4: If my child has been vaccinated with an ineffective vaccine, does he or she need to be re-vaccinated with an effective one?
In general, because administering an expired or improperly handled may not provide protection from the disease for which the vaccine was intended, the vaccination should be repeated. It is safe to repeat the vaccination, and these can be given either immediately for inactivated vaccines or after 28 days for live virus vaccines. However, the risk of different vaccine preventable diseases varies by age, so not all vaccinations need to be repeated. There are some diseases for which a child’s immunity and need for revaccination can be determined with a blood test, for example measles, rubella, hepatitis A, hepatitis B, and varicella. Decisions to revaccinate should made in consultation with health professionals in the EPI clinic.
Q5: What does “minimal safety risk” really mean?
As far as we know, vaccines that are stored out of their required storage temperature range or that have passed their expiration date do not become contaminated or toxic; rather, the issue is that they cannot be guaranteed to be potent. All vaccines carry some risk of side effects such as an allergic reaction to a component of a vaccine. However, administering an expired or improperly stored vaccine should not pose any additional risk or toxic reaction beyond the normal risk of side effect.
Q6: If a child is vaccinated with ineffective vaccines, will this result in any harmful outcomes?A child being administered an improperly stored vaccine is extremely unlikely to get sick as a result of receiving the vaccine. However, if the vaccine had lost potency due to expiration or improper handling, the child could be harmed if he or she gets infected later in life because the impotent vaccine provided no protection from the disease for which the vaccine was intended. This situation would be the same as if the child had never received the vaccine.
Q7: Should we have our kids vaccinated?
Yes. Children in China, as children in the rest of the world, need vaccines to protect them from vaccine preventable diseases. The Chinese immunization program protects children from 12 infectious diseases. All children, except for the very small number of children who cannot be vaccinated due to a medical reason, should be vaccinated with vaccines used in the routine program. Vaccination is the safest way to protect children from vaccine preventable diseases.
