I travel often into mosquito vector regions. For example earlier this year I was in Laos in February and Sri Lanka in March. Mosquitoes appeared without fail at dusk and dawn but neither country appears to have discovered window or door fly screens. I have 'interesting' blood" leading to a reduced immune system. That means I am theoretically more likely to catch nasty things as I travel. I also cannot have live virus inoculations such as Yellow Fever.
There are medications such as Malarone for protection against malaria but it can have side effects and malaria is only one of a host of mosquito vector diseases: Dengue Fever, Ross River Virus, West Nile Virus and Yellow Fever are just some of them. For that reason I try to totally avoid being bitten by mosquitoes.
My methods may appear OCD or over the top. I hope I help with some tips, even if you don't do everything I do. It has kept me safe without a single infection by mosquitoes as I wander the world.
I make sure that there are no mosquitoes in the rooms I stay in and demand insect spray from the proprietors if necessary. I usually have it with me as insect spray is one of the first things I buy in a new country on arrival.
I wear a hat or cap (I am bald), long-sleeved shirts and long trousers at dawn and dusk, with as little skin left exposed as is reasonably possible. My clothing is lightweight in the tropics, but not so light that mosquitoes can drill through it.
After my morning shower I apply a light skin lotion as a
base. Over that, if appropriate to the climate, I apply a sunblock.
I finish with a light coating of 80% DEET to all exposed areas,
including at least the face, back of the neck, ears and ankles. That
strength of DEET is effective but can also cause skin problems;
applying the skin lotion first allows a more even spread of a thin
layer and minimises the side effects. This is the one I use, but any brand should do the job: