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Millions of people are now being immunized with the new Pfizer-BioNTech and Moderna mRNA vaccines. Are they effective? Are they safe? Infectious disease and global health expert Carlos del Rio, MD, of Emory University, answers frequently asked questions.
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The US has authorized two vaccines against COVID-19. Both are mRNA vaccines, and data show they are highly effective. But physicians and patients have many important questions about these vaccines. So we reached out to infectious disease and global health expert Dr Carlos del Rio for evidence-based answers.
Can I take the vaccine if I have immune disease, cancer or am on immunosuppressive drugs?
There's no contraindication in my mind to take the COVID vaccine. What we don't know is how good your response to the vaccine is. So, unfortunately, you know, clinical trials did not include people with immune-compromised states, so we don't know if it's going to be, if the response is going to be as good as it was in other people.
Can I take the vaccine if I'm pregnant or breastfeeding?
Women who are pregnant or breastfeeding were not included in the clinical trials. Having said that, there were women in the clinical trials that became pregnant, and they're being followed closely. The American College of Obstetrics and Gynecology and the Society for Maternal Fetal Medicine, and the CDC have put a statement saying that there is no reason why a woman who's pregnant or breastfeeding should not receive the vaccine. And I would tell you personally, both my daughter and my daughter-in-law are breastfeeding, and my daughter-in-law already received the vaccine.
Can I take the vaccine if I have allergies?
Depends on what you mean by "I have allergies." You know, some people say, I'm allergic to peanuts. I'm allergic to dye. I'm allergic to, it depends what you're allergic to. If you're allergic to one of the components of the vaccine, you definitely should not receive it. But if you have an allergy, you know, you break out when a bee stings you, you have no problem. You are okay receiving the vaccine.
What if I have a history of severe allergic reactions?
What I've seen so far is that allergic reactions and anaphylactic reactions are exceedingly rare. What I tell people is if you had previously a severe allergic reaction to a vaccine or if you have a situation in which you have had an anaphylactic reaction, you need, in other words, you carry an EpiPen with you. You need to tell this to the place where you're going to get vaccinated, and they will observe you more closely. They'll be careful to have you under observation and have the EpiPen and all the other things ready to go.
Can I take the vaccine if I already had COVID-19?
You can take the vaccine, and we recommend that you take the vaccine. But what we're doing right now is we're telling people, again, because there's a limited vaccine supply, we're telling people, if you had COVID-19, documented COVID-19, you don't necessarily need to get the vaccine right away. We're even telling people wait for 90 days or so, so your immune system is not as reactive yet, you know. But the reality is we want you to get the vaccine because we know from the vaccine studies that some people were enrolled when they had prior COVID, and they were also further protected by having the vaccine.
Is either of the vaccines better than the other? And can I switch between doses?
I was talking to a friend of mine, and I say, you know, it's a little bit like comparing Pepsi and Coke. The reality is they're different brands, but they're essentially very similar; right? They have slight differences, but the efficacy is very similar. The safety profile is very similar. Having said that, what we are recommending in the US, if you got your first vaccine as Pfizer, you should get your second vaccine as Pfizer. If you got your first vaccine as Moderna, you should get your second vaccine as Moderna. Interestingly, UK is not saying that. The UK is saying, we don't care what you got, you know, you can take either vaccine. I don't know what the answer is. I'm a more traditionalist. I got Pfizer as my first dose, and I want to get, I'm going to get Pfizer as my second dose.
Can I only take one dose to minimize risk?
The UK and now the US is discussing whether we should just give one dose instead of two doses. What they're talking about is delaying the second dose. And the reason behind that is trying to vaccinate more people with just one dose rather than a small number of people with two doses. We don't know the answer to that. It will not minimize your risk. It may actually increase your risk of getting disease later on. I mean, the reason for the second dose is to actually enhance your immune response. So my recommendation at this point in time, and I'm talking to, about what would I do for myself? I would take both doses. So it's very hard for me to tell people, oh, you know, one dose is fine when myself, I want to get two doses.
I received the first dose and still got COVID-19. Should I take the second dose?
You know, that's a really good question. I've seen this over and over. I had some people, questions come up all the time. I had a colleague of mine, you know, he got vaccinated on Saturday. He started feeling bad on Monday. And by Tuesday he was diagnosed with COVID. That means he simply had already COVID and was incubating, and the vaccine doesn't work right away; right? You need some time for your immune system to produce antibodies and start getting you a certain degree of protection. Probably about two weeks after the first dose, you start getting, 10 to 14 days, you start getting some protection. Yes, you need to take the second dose. But a good question is, when do you take the second dose; right? And my recommendation is that you take the second dose, if you had the COVID right away after you got the first dose, probably take the second dose either 21 to 28 days after the first dose. You may want to delay it a little longer, if possible. But other than that, I see no reason why you shouldn't take the second dose.
I missed my appointment for the second dose. How late can I still get it?
Well, you know, we would like you to get the vaccine, the seconds dose as soon as possible. The UK is even talking about delaying it for 12 weeks. So, you know, is it possible to delay for 12 weeks? We don't have a lot of data, but I suspect you probably can delay it. I mean, this idea, both vaccines are essentially, you know, Pfizer is zero and 21 days. Moderna is zero and 28 days. You can probably go, because of what we know about the immune response, you can probably extend that easily a couple, you know, 4, 8, 12 weeks more, which is what the UK is doing.
Are there natural ways to improve my immunity?
Well, you know, there are no really good natural ways to improve your immunity. But there are natural ways to improve your health, and that will improve your immunity and that will decrease your risk of getting severe COVID in case you get COVID. So my recommendation, overall, is improve your health overall. Control your blood pressure. Control your weight. Control your sugar. And if you do all those things, your overall life expectancy is going to be better. So that's how you improve your immune system, by eating healthy, by exercising and by leading a healthy lifestyle.
Will virus mutations make the vaccine less effective?
Well, there could be viral mutations that make the vaccine less effective. Up to now the viral mutations we've seen do not appear to make the vaccine less effective, again, because the vaccine produces broadly neutralizing antibodies. So there's more than one epitope that the vaccine is directed against. But there could potentially be a mutation that will make the vaccine not be effective. You know, RNA virus, that's what they do for a living. They actually mutate continuously. They're changing all the time. The more rapidly we can stop transmission and vaccinate people, the less likely the virus is going to be mutating.
How long does protection last?
People in the clinical trials, in phase 3 trials are going to be followed for a total of two years, trying to understand how long does protection last? What we know so far from people that were enrolled in the phase 1 studies, we know that up to now they're still immune. So we know that at least six months later you still have immunity to this virus.
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