The US Center For Disease Control maintains an updated list of medical advice for those traveling to Belgium.
There are no particular health concerns in the Benelux — if you don’t count the “risk” in Amsterdam and other Dutch towns of occasionally breathing in a whiff of someone else’s legally tolerated hashish smoke (and of course they’d likely argue that it’s perfectly healthy). You will encounter few other health problems when traveling. The tap water is safe to drink, the milk is pasteurized, and healthcare is excellent.
No health and vaccination certificates are required. You don’t need any shots before your trip, but if you suffer from a chronic illness, consult your doctor before your departure. Pack prescription medications in your carry-on luggage, and carry them in their original containers, with pharmacy labels — otherwise they won’t make it through airport security.
General Availability of Healthcare
The state-owned healthcare systems in the Benelux lands are among the world’s best, even if they have begun to show signs of the strain of universal healthcare for all. It’s easy to get over-the-counter medicines for minor ailments, and both local brands and generic equivalents of most common prescription drugs are available.
Here is a link to the US State Department Travel Advisory for Belgium for the latest information on traveling to Belgium.
Belgium is generally safe — even the big cities are low-crime areas. However, Belgium has experienced a creeping spread of drug-related crime, and crimes committed by some poorly integrated members of immigrant communities. In Brussels, the Métro has been plagued by muggers, and though increased police presence and video surveillance have brought this under control, it’s still better not to venture alone into deserted Métro access corridors after dark; when other people are around, it’s generally safe.
Both Brussels and Antwerp have well-defined red-light zones, in which more than a little caution is in order. Don’t confuse these places with the Red Light District up the road in Amsterdam, which is a pretty big tourist attraction in its own right, and mostly safe for casual visitors. Brussels’s red-light zone in particular is a creepy, low-life zone, and though Antwerp’s is not quite so bad it’s still not really a place to go for sightseeing. Bruges and Ghent have only minimal facilities of this kind, so this is not a factor there.