But she stressed it does not protect women against every strain of the HPV virus, and said it was vital they continue to attend screening.
Dr McKenzie added: "They must understand that the vaccine is fantastic news for preventing cervical cancer, but it can only be combated by using cervical screening and the vaccine.
"So when they are called for screening aged 20 they really must come along whether they have had the vaccine or not."
The number of girls aged between 20 and 25 who come forward for cervical smears is already declining.
Some fears have been expressed that the vaccination programme will cause even fewer to attend screening, while questions have also been asked about why so much money is being spent on saving the lives of less that 100 Scottish women a year.
Denise Burgin, whose daughter Shelley died after being diagnosed with cervical cancer when aged just 27, said she was in no doubt the injections were worthwhile.
Mrs Burgin, from Dollar in Clackmannanshire, said: "If we can just help one other person and prevent them from having to go through what we have gone through, then her death will not have been in vain."
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