Lugelo Ahmed, Hampson Katie, Czupryna Anna, Bigambo Machunde, McElhinney Lorraine M, Marston Denise A, Kazwala Rudovick, Lankester Felix
Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Dar es Salaam, Tanzania.
Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom.
Front Vet Sci. 2021 Sep 29;8:728271. doi: 10.3389/fvets.2021.728271. eCollection 2021.
Thermostable vaccines greatly improved the reach and impact of large-scale programmes to eliminate infectious diseases such as smallpox, polio, and rinderpest. A study from 2015 demonstrated that the potency of the Nobivac Rabies vaccine was not impacted following experimental storage at 30°C for 3 months. Whether the vaccine would remain efficacious following storage under more natural, fluctuating temperature conditions remains unknown. We carried out a randomised controlled non-inferiority trial to compare serological responses in dogs following vaccination with doses stored under cold chain conditions with those stored within a locally made Passive Cooling Device ("Zeepot") under fluctuating temperature conditions. Nobivac Rabies vaccine was stored under either cold-chain conditions or within the Zeepot for 2 months. Daily ambient temperatures and temperatures within the Zeepot were recorded every 3 h. Following storage, 412 domestic dogs were randomly assigned to receive either cold-chain or Zeepot stored Nobivac Rabies vaccine. Baseline and day 28-post vaccination blood samples were collected. Serological analysis using the Fluorescent Antibody Virus Neutralisation assay was carried out with a threshold of 0.5 IU/ml to determine seroconversion. In addition, the impact of dog Body Condition Score, sex, and age on seroconversion was examined. The serological response of dogs vaccinated using Nobivac Rabies vaccine stored within the Zeepot was not inferior to the response of dogs vaccinated using cold-chain stored vaccine (z = 1.1, df = 313, -value = 0.25). Indeed, the 28-day post-vaccination group geometric mean titre was 1.8 and 2.0 IU/ml for cold-chain vs. non-cold-chain storage, respectively. Moreover, the percentage of dogs that seroconverted in each arm was almost identical (85%). There was a positive linear trend between Body Condition Score (O.R. 2.2, 95% CI: 1.1-5.1) and seroconversion, suggesting dogs of poor condition may not respond as expected to vaccination. Our study demonstrated the potency of Nobivac Rabies vaccine is not impacted following storage under elevated fluctuating temperatures within a Zeepot. These results have potentially exciting applications for scaling up mass dog vaccination programmes in low-and-middle income countries, particularly for hard-to-reach populations with limited access to power and cold-chain vaccine storage.
耐热疫苗极大地提高了大规模消除天花、脊髓灰质炎和牛瘟等传染病计划的覆盖范围和影响力。2015年的一项研究表明，诺必威狂犬病疫苗在30°C下实验储存3个月后效力并未受到影响。在更自然的、温度波动的条件下储存后该疫苗是否仍有效尚不清楚。我们进行了一项随机对照非劣效性试验，以比较在冷链条件下储存的剂量与在当地制造的被动冷却装置（“Zeepot”）中在温度波动条件下储存的剂量接种疫苗后犬类的血清学反应。诺必威狂犬病疫苗在冷链条件下或在Zeepot中储存2个月。每3小时记录一次每日环境温度和Zeepot内的温度。储存后，412只家犬被随机分配接受冷链或Zeepot储存的诺必威狂犬病疫苗。采集基线和接种后第28天的血样。使用荧光抗体病毒中和试验进行血清学分析，阈值为0.5 IU/ml以确定血清转化。此外，还研究了犬的身体状况评分、性别和年龄对血清转化的影响。使用储存在Zeepot中的诺必威狂犬病疫苗接种的犬的血清学反应不劣于使用冷链储存疫苗接种的犬的反应（z = 1.1，自由度 = 313，p值 = 0.25）。实际上，接种后28天组的几何平均滴度在冷链储存与非冷链储存时分别为1.8和2.0 IU/ml。此外，每组中血清转化的犬的百分比几乎相同（85%）。身体状况评分与血清转化之间存在正线性趋势（比值比2.2，95%置信区间：1.1 - 5.1），表明身体状况不佳的犬可能对疫苗接种的反应不如预期。我们的研究表明，诺必威狂犬病疫苗在Zeepot内温度波动升高的情况下储存后效力不受影响。这些结果对于扩大低收入和中等收入国家的大规模犬类疫苗接种计划具有潜在的令人兴奋的应用，特别是对于难以接触到、电力供应有限且无法进行冷链疫苗储存的人群。
