New York, Jul 25 (IANS): With the global pandemic still in full swing, scientists around the world are working to develop an effective vaccine for Covid-19 virus in record time but they don't all agree on how to get there and what "effective" really means.

In the study, published in the journal Chemical & Engineering News (C&EN), the experts spoke with researchers, doctors and business leaders to shed light on some of the challenges vaccine developers are facing.

"As of mid-July, the World Health Organisation (WHO) reported that over 160 vaccine programmes were in progress, an unprecedented effort toward a common goal," wrote the study author Ryan Cross from C&EN in the US.

For SARS-CoV-2, the virus that causes Covid-19, that part is the spike protein, which the virus uses to attach itself to human cells.

Both types of methods can be time-consuming, and traditional approaches are potentially dangerous because companies need to grow large amounts of virus.

This has caused some scientists to turn to experimental gene-based vaccines, the experts said. Researchers put the genetic code for the spike protein into harmless viruses that act as vessels, or simply use DNA or RNA to deliver the genetic information to human cells.

Human cells would use these instructions to make the spike protein, which would trigger an immune response.

These types of vaccines are very fast for scientists to design and make, but the technology is largely unproven, and it remains to be seen whether these kinds of vaccines are effective, Cross wrote.

Furthermore, there are many different modifications that scientists can make to the spike protein, which could change how our immune systems respond to the real virus.

According to Cross, vaccine makers are focusing on the ability of candidates to produce high levels of neutralizing antibodies that would prevent the virus from entering cells.

But this area of vaccine research also faces challenges. For example, the methods for quantifying the antibody response in the laboratory are not ideal.

In addition, it's unclear just how much neutralization is good enough and for how long the effect would last.

"If antibody levels aren't high enough, a person might only be left with partial immunity, which could prevent severe symptoms but still leave them with the ability to infect others and what works in one person might not work well in another," Cross said.

Questions about safety still loom, and experts warn that moving too fast with an unsafe vaccine could shake public confidence.