Melinda Gates and immunisation
I had expected one of the world's richest women to arrive in a convoy, with police outriders, akin to those that transport visiting heads of state. So it was with some surprise that just two vehicles drove into a health clinic in Nairobi that was offering immunisation against pneumonia.
Melinda Gates emerged, smiling, from the back of a nondescript Toyota mini-van, and went straight into meeting nurses and mothers at the Westlands Health Centre.
Mrs Gates's arrival may have been low-key, but her influence is immense. Together with her husband Bill, she set up the Gates Foundation and has so far donated $23bn to fund global healthcare. The Gates have pledged to give away 95% of their personal wealth.
That will still leave them with quite a bit left over , and you could argue that it is wrong that one couple were able to accumulate so much money.
Nonetheless, it is a remarkable piece of philanthropy , and it is hard to argue with the Gates Foundation core statement that "every life has equal value", or its aim of lifting people out of "hunger and extreme poverty".
The Gates Foundation drives research and development of new vaccines for the developing world. That is why Melinda Gates was in Nairobi to witness the roll of the pneumococcal jab. It protects against 10 strains of pneumococcal bacteria, responsible for the majority of pneumonia deaths.
Mrs Gates said: "Vaccines are the single most cost-effective tool we can use to save children's lives. Bill and I think it is the most incredible investment you can make."
But she warned the field of global immunisation faced a funding shortfall of $3.7bn in coming years, and said unless governments committed more money to immunisation then children would continue to die from preventable illnesses.
She said: "I am extremely concerned about the $3.7bn shortfall. The chances of getting pneumonia here in Kenya is very high - around 20,000 children a year die from it. So when I think about that I try to think about a child living because of the vaccine. "
We filmed Mrs Gates on her tour of the health centre. A mother of three school-aged children, she seemed completely at ease surrounded by dozens of mums and infants. In the immunisation room, Mrs Gates held a six week old orphan being given her pneumonia jab and polio drops.
I doubt many of the mothers at the clinic recognised Mrs Gates or knew of her pivotal role in securing new vaccines for countries like Kenya. Understandably, they were focussed on the task in hand - getting their children protected from pneumonia. You can view my report on pneumonia vaccines here.
Meanwhile Bill Gates will be raising the issue of immunisation later this week at the World Economic Forum at Davos, Switzerland. Mr Gates will be urging world leaders to commit more foreign aid to immunisation.
Click below to see my interview with Melinda Gates.