TL;DR: Yes, you still have to wear a mask (N95 NIOSH, KN95, 3-ply etc.), here is the explanation:
While the Pfizer/Biontech and the Moderna vaccines are 95 %, respectively 94.1 % effective, this statistic just expresses the ability to stop symptomatic COVID-19. What this indicates is that while a totally vaccinated individual is safe from getting ill with COVID-19, he or she can still be a carrier and transmit the virus asymptomatically – similar to how individuals without symptoms had the ability to infect others before there were vaccinations available.
Mucosal infection and spread
This additionally complies with the function of these vaccines. To stimulate an effective immune response, the injection is placed deep into the upper arm’s muscle tissue. This stimulates the immune system to create antibodies that correctly recognize special parts of the virus and attack it. But, although antibodies flow through the blood, the coronavirus can still spread fast in the nasal passage until sufficient counts of antibodies can destroy it there.
Mucosal vaccines, like nasal spray vaccinations for influenza, are far better than intramuscular shots at avoiding transmission of respiratory system infections. Until such a mucosal vaccination is readily available for COVID-19, you can quickly spread the infection through your nose while immunized, even if the virus won’t make you sick anymore.
Protection, distance, hygiene
That is why it is extremely important that up until the vaccination has been provided to a sizeable amount of people, that all of us remain to adhere to public health instructions to secure the health of those around us. This consists of using a mask or respirator, e.g. a KN95 respirator, keeping the minimum distance (> 6 feet) from people, avoiding gatherings of people, washing hands frequently, complying with CDC and adhering to quarantine guidance (e.g. after direct exposure to somebody with COVID-19, re-entering the States from abroad, etc.).