A vaccinologist says we shouldn't rely on the vaccine alone to protect ourselves from COVID-19.
An Air NZ flight attendant who initially returned a negative result, tested positive for COVID-19 on Sunday.
Despite having received a shot of the Pfizer vaccine days earlier, Auckland University associate professor and vaccinologist Helen Petousis-Harris says it doesn't protect us from the virus straight away.
"When a person gets the first dose of vaccine, the immune system kicks in almost straight away. However, it takes a few days before the protection starts to kick in," Petousis-Harris says.
"This is because your body needs to alert and gather the various specialised cells needed to make the COVID-specific cells and antibodies. Once these are assembled, immunity grows over time."
The Pfizer vaccine requires two doses taken at least 21 days apart. Petousis-Harris says after the second dose, 9 out of 10 people should have developed full protection against the virus.
University of Canterbury Associate Professor Arindam Basu says the flight attendant could have contracted the virus before receiving the vaccine, despite initially returning a negative result.
"From the time of first infection, it takes anywhere between 0-14 days for the manifestation of COVID-19 to turn out positive, with an average of 5-7 day, and this is regardless of the vaccination," he says.
"So, after the first dose of vaccine, or even after the second dose of vaccine, one can turn out to be positive."
Psychologist Dr Sarb Johal says the vaccine is not a silver bullet in protecting us against the pandemic.
"We need to remember the vaccine is best thought of as an additional layer of protection," he says.
"Physical distancing, masking, continued washing of hands and tracking our movements are key behaviours that help to keep us safe."
Dr Johal says we shouldn't rely on the vaccine alone to protect ourselves against the virus.
"The vaccine is not a silver bullet for the pandemic...
"Vaccines are just one part of the multiple layers we are going to need to use for a considerable period of time."
It is not possible the crew member caught the virus from receiving the vaccine as it does not contain any live, dead or deactivated virus, according to the Ministry of Health.