Vaccine clinical trials in low- and middle-income countries: a brief review of standard, newer and proposed approaches.

Of the vaccine trials done worldwide, only a small proportion is conducted in LMICs, but this is likely to increase as more research experience and infrastructure is developed. At present, the majority of vaccine trials follows the standard paradigm of fixed phase 1 to 3 trials, the latter with clinical endpoints, or immunobridging studies when a valid immunocorrelate of vaccine protection exists. Other study designs may help facilitate the generation of data toward licensure of and recommendations for needed vaccines. Increased international collaboration is needed for local capacity building and regulatory oversight to ensure that all studies are conducted under good clinical practice.