LO sleeping longer hours after 2m vax. Question on whether or not to feed more oz or wake him?

My LO had his first round of 2m vaccinations yesterday and since he's been sleeping longer hours. Thankfully he didn't spike a fever but I was wondering how long the sleepiness should last?

He usually eats about 5oz of formula every 4 hours, rarely 5 hours. But now he's sleeping longer and ends up eating at about every 6 hours. Should I wake him to eat or let him rest? I may give him more formula if he's going to be doing these long stretches of sleep. Would that be too much for his little tummy?