Coronavirus: exempt emergency vaccines from late-stage clinical trials, Chinese health official urges WHO
- Zeng Yixin says WHO should consider replacing late-stage human trials with data relating to neutralising antibody levels
- WHO experts have discussed whether and how to move from clinical endpoint data to correlating measures of immunity
Zeng Yixin, vice-minister of the National Health Commission, said the WHO should consider replacing phase 3 human trials with data relating to neutralising antibody levels – an indicator of immunity – generated by the vaccines under consideration to scale up production.
Five more vaccines – including those by CanSino and Anhui Zhifei Longcom Biopharmaceuticals – are also applying for WHO emergency use listing.
In the past, antibody levels in blood have been used to indicate vaccine effectiveness.
For example, annual licensing of the seasonal flu vaccine booster is based on how well it generates a threshold of antibody levels.
Researchers around the world are still studying immune “correlates of protection” that would preferably and reliably predict protection against Covid-19.
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WHO experts met last month to discuss whether and how to move from clinical endpoint data to correlating measures of immunity.
Experts say that such surrogate data can be used in bridging vaccines for additional groups, such as the elderly or adolescents, but a standardised substitute biomarker to evaluate the effectiveness of a new vaccine was needed since the data could vary between platforms of vaccine and even between vaccines within the same platform.
Confidence in Covid-19 vaccines could be affected if a correlate that is not very rigorous was chosen or the vaccine did not work as well as expected, the meeting was told.
Mainland researchers such as Zhu Fengcai, deputy director of the Jiangsu Centre for Disease Prevention and Control, have been studying to how to use surrogate endpoint data from immunity of Covid-19 vaccines that have released trials results to predict the protection of Covid-19 vaccines.
In the early stage of the pandemic, China responded with vaccine development using different technologies starting as early as February last year, including the more advanced mRNA platform.
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But since China has now largely contained Covid-19, the country cannot test vaccines within its own borders and must instead conduct phase 3 trials overseas.
This involves tens of thousands of participants and is a process described by industry insiders as long, expensive and challenging.