Why are women so prominent in vaccine development?

Here is my Bloomberg column arguing that they are prominent in vaccine development, excerpt:

Then there is the vaccine from Novovax, which is based in Gaithersburg, Maryland. The Novovax results are not yet published, but early word is that they are very promising. This vaccine also is based on new ideas, using an unusual moth cell system to crank out proteins in a highly innovative manner.

Novovax’s team is led by Nita Patel, an immigrant from Gujarat, India. Her vaccine team is identified as “all-female.” Patel is from a very poor family; her father almost died of tuberculosis when she was 4 years old, and she often had to beg for bus fare.

Immigrants too, and there is much more evidence at the link.  In fact women have been prominent in vaccine research for a long time.  But why vaccines?  What is the best hypothesis here?