Part of a continuing series.
We’re continuing to answer readers’ virus and vaccine-related questions. Have a question of your own? Ask it in the form at the bottom of this article.
Is it OK to get one dose of Pfizer vaccine and then a second dose of Moderna, or the other way around? Can I go to different clinics for each dose?
No, and no. If your first vaccine dose is from drug manufacturer Pfizer, your second one needs to be from Pfizer too, said Dr. Joe McLaughlin, a state epidemiologist. Same goes for Moderna. That’s because although both are relatively similar mRNA vaccines, it’s important to get vaccinated in the way the vaccines were studied for safety and efficacy.
Currently in Alaska, you also need to go to the same place where you got your first dose to get your second, McLaughlin said.
“If you’re going to be one of the lucky people to get vaccinated, you need to plan ahead and make sure you’re able to go back to the same exact clinic or location that you got your first dose for your second dose,” he said.
The reason for that has to do with making sure there is a second dose set aside for you. Clinics order second doses based on how many first doses they receive and distribute. Most clinics and distribution sites will ask you to sign up for your second dose when you come in for your first.
How accurate are antibody tests?
Antibody tests — also called serology tests — can be use to determine whether you had a previous coronavirus infection by checking for an immune response to the virus built up in the bloodstream. But the accuracy of these tests really depends on the manufacturer, which vary widely, McLaughlin said.
Generally, antibody tests are nowhere near as sensitive or specific as a common nasal swab (polymerase chain reaction) test used to check for active infections, he added.
The federal Centers for Disease Control and Prevention is currently studying the performance of commercial serology tests, like the ones you can now purchase over the counter at places like Fred Meyer.
“Nothing is 100% in terms of serology,” said Jayme Parker, who heads up the state public health labs, noting that test accuracy ranges from 50% to 90% accurate. That wide range makes the results difficult to interpret.
A serology test can produce a false positive if a patient has had other coronaviruses, like the one that cause the common cold, Parker said. And some patients don’t produce enough detectable antibodies from their infection to be picked up by these tests, depending on their sensitivity.
“So, it definitely sometimes leads to more questions than answers with serology tests,” she said.
Can proof of vaccination be used as a substitute for a negative test result when traveling to Alaska?
No. Current state emergency orders and travel mandates in Alaska do not treat travelers differently based on their vaccination status, health officials say.
That means that all nonresidents traveling to Alaska are still required to arrive with a negative result from a COVID-19 test taken within three days of when their plane to Alaska departs, or pay $250 for a test when they land in the state and be willing to quarantine until they receive a negative result.
Alaska residents have the additional option of quarantining for two weeks in lieu of testing, and their airport COVID-19 test is free.
“You do need to continue following all the mitigation efforts even after you’re vaccinated,” said Tessa Walker Linderman, who helps lead the state’s vaccination effort, during a recent meeting.
That’s partly because data on whether the recently approved COVID-19 vaccines thoroughly protect against contagious asymptomatic infections is still being collected.
Dr. Anne Zink, the state’s chief medical officer, added that the reason why it’s so important that travelers continue to closely follow posted travel mandates and avoid being around people post-travel is that Alaska has not yet detected the highly contagious virus variant first detected in the United Kingdom, and she wants it to stay that way.
About half of all COVID-19 infections are asymptomatic, she added.
If I get the vaccine, when will I start being immune to COVID-19, and how long will it last?
It takes about two weeks after receiving the second dose of vaccine to develop maximum immunity from the vaccines, health officials stay. As far as how long immunity conferred by the vaccine will last, that’s still being determined, McLaughlin said.
“That’s something we’re not going to know until we have empirical data to really demonstrate one way or another,” he said, adding that the hope is that immunity will last at least a year.