What to say about worms?? *sigh*
First, I am not a vet. this is just info I have gathered and thoughts on it. please talk to your vet.
There are 4 common worms when talking dog. here are some links for more info on the common types.
Very few dewormers get them all and then only at certain life stages.
what we like and use below
Some dewormers are safe for young pups but are only good for round and nonresistant hooks (pyrantel pamoate).
Other dewormers are stronger and multiple days but can only be used on weaning aged pups (fenbendazole). And good for Rounds, Hooks, Whips and 1 type Tape)
Some have multiple active ingredients so can get more type (Drontal Plus praziquantel/pyrantel pamoate/febantel). Round, Hook, Whips and Tape but is RX.
There are no worm free dogs/puppies. even if tests come out negative (clear of worm eggs) that means they don't see any that day. Deworming is an ongoing thing.
Worms have been around since before we knew what a worm was. they are survivors. so, there is always a chance of dewormer resistant worms.