Massive immigration from Haiti. It's safe to say the Haitian government doesn't care for its people at all. Look at malaria. It was almost erradicated in the DR except near the border. As anyone knows, malaria infected mosquitos don't stop at the border. Now there are malaria pockets in various parts of the DR again and they go hand in hand with large conglomerations of Haitian immigrants. It turns out that the Haitian government did almost nothing to eliminate malaria in Haiti while the DR was busy erradicating the disease. Malaria risk is in the entirety of Haiti. Hispaniola is now the only island in the Americas with the disease. It has been erradicated in every other island in the Caribbean, from Cuba and Jamaica to St Lucia and Barbadoes.
Same happen with cholera, though that was introduced (mistake) in Haiti by the UN. In a small amount of time it became an islandwide risk. All Dominican airports still have how to prevent cholera papers on the walls. Guess how it made it to the DR. No other island in the Caribbean has cholera, as far as I know.
A few years ago there was an outbreak of polio in Jarabacoa. That was an entirely Dominican outbreak, Haitians had nothing to do with that. However, the Ministry of Public Health quickly sent a team to Jarabacoa to vaccinate for free against polio and keep track of those infected. The outbreak was contained and there is practically no polio risk in the DR. Had it happened in Haiti and I have serious doubts the Haitian government would do anything to contain it. Too much experience of an outbreak that could had been contained only to grow into a nationwide risk.
Look what happen today, the Haitian government rejected the 100,000 anti-Covid vaccines that the Dominican government donated to them. I'm sure all Haitian politicians and their families are already vaccinated. I guess that and the elite is all that matters over there. Anyway, the rejected vaccines are added to the Dominican donation to Guatemala.
Fuentes cercanas al proceso aseguraron a Diario Libre que las autoridades haitianas tomaron esa determinación
diariolibre.com