In the majority of the population, the first dose of the vaccine prompts an initial immune response providing only partial protection. Depending on the type of vaccine, protection starts after about 2-3 weeks from the first dose, thus keeping the risk of COVID-19 still consistent, albeit reduced.
The second dose of vaccine is therefore required to increase the immune response and obtain optimal vaccine protection.
In the case of people with SARS-CoV-2 infection/disease confirmed by a third generation molecular or antigen test after the first dose of the vaccine, the infection itself represents a powerful stimulus for the immune system, which adds to the one provided by the first dose of vaccine.
In light of this and considering that natural infection initiates a specific immune response to the virus, it is not recommended to administer the second vaccination dose to these people. Partial vaccination and subsequent infection do not preclude a possible booster dose of COVID-19 vaccination in the future, if data on duration of immune protection indicate such need.