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Why getting just one Pfizer or Moderna vaccine is not enough

If you still need to get your second dose, you are not fully protected & should continue all safety precautions as if you were completely unvaccinated, the CDC says.

SACRAMENTO, Calif. — As more Californians become eligible to receive the coronavirus vaccine, many ABC10 viewers have been wondering what happens between their first and second shots, if they get the Pfizer or Moderna doses.

The answer is clear according to the Centers for Disease Control and Prevention (CDC): If it has been less than two weeks since your second shot, or if you still need to get your second dose, you are not fully protected and should continue all safety precautions as if you were completely unvaccinated.

According to research published on the BMJ, the immune response for both the Pfizer and Moderna vaccines are much stronger after the second shot and delivered longer-lasting immunity -- from 52% to 95% effective, according to one study on the Pfizer-BioNTech vaccine.

“People who are not fully vaccinated or are in between their first and second vaccine should keep wearing masks, washing hands, and watching their distance until the vaccine has been widely administered,” said a spokesperson for the California Department of Public Health (CDPH).

The San Joaquin County Public Health Department concurs, saying that despite some evidence of a partial vaccination’s efficacy, it is not as highly effective as being fully vaccinated.

“The guidance is that one should get both doses, based on the vaccine schedule (for Pfizer, 3 weeks apart; for Moderna, 4 weeks apart), for maximum efficacy again severe illness, hospitalization, and death from COVID,” a San Joaquin County health official wrote in an email.

Asked if partially-vaccinated people could mix with other partially-vaccinated or fully-vaccinated people, San Joaquin County Health officials say it’s better to be safe than sorry.

“We recommend that [partially-vaccinated individuals] continue to practice safety precautions as if they are not vaccinated. The partial vaccinations status raises concern for risk of coronavirus variant development among those in the middle of building immunity and interacting with those who are not immune or are infected during this time,” SJCPH officials said.

Citing the CDC, the CDPH went even further, suggesting that even after being fully vaccinated, people should still take precautions in public places like wearing a mask, staying six feet apart, and avoiding crowds and poorly ventilated spaces until more is known.

Overall, there is no specific guidance on behaviors in between vaccine doses from the CDC, but local health experts agree that maintaining safety practices is emphasized. As both COVID-19 and its approved vaccines continue to be studied, new guidance could be available in the future.

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