Antibody-dependent enhancement.

The failure of the RSV vaccine highlights the importance of fully understanding the immune response before progressing to clinical trials.

Another way a vaccine can cause harm is through antibody-dependent enhancement (ADE). This means that antibodies produced against the virus also bind to receptors on host cells, which ultimately means that the virus is more likely to infect them.

Experts have observed this effect in vaccines against Dengue, Ebola, and HIV, and in a coronavirus in cats.

However, several studies of SARS-CoV vaccines in rhesus monkeys – a much closer relation to humans – have shown no evidence of ADE.
Slow is fast

As well as the scientific roadblocks, there are many ethical hurdles to overcome before performing studies of experimental vaccines in people; studies that may pose significant risks. Dr. Green says that scientists must way up these “extreme risks” against the potential benefits.

The take-home message of the article is that while time is of the essence, it is essential to ensure the safety of any potential vaccine.

It is vital to ensure the safety of any vaccine, including a full investigation of its potential adverse effects. Rushing this process could have catastrophic consequences, says Dr. Green, who recommends the application of the axiom ‘Fast is slow, and slow is fast’ to COVID-19 vaccine development.