The FDA has now authorized three COVID-19 vaccines. Both of the first two authorized vaccines rely on an immunity-building strategy that hasn’t been used in any other vaccine. As many of us start rolling up our sleeves to get a shot, here are answers to some of the most frequently asked questions.
What is mRNA? Why does it matter?
All previous vaccines have been based on weakened virus molecules or proteins from the disease (pathogen) that our immune systems can easily overcome while learning to recognize it. The new vaccines from Moderna and Pfizer — the first two to make it to market so far in the U.S. — contain mRNA (messenger RNA), which is a genetic template that instructs our cells to build the viral proteins that our immune systems can then recognize. Its main perk is that by allowing our bodies to produce the proteins (rather than growing them in a lab like in traditional vaccines), it slashes the time it takes to produce the vaccine (as done in the past) in the lab. For nearly 20 years, researchers have been interested in using mRNA in vaccines. Some were even tested in early clinical trials for rabies, influenza and Zika. However, the vaccines for COVID-19 are the first mRNA vaccines ever authorized by the FDA. This long history of studying the mRNA concept is why the vaccine could be developed so quickly. mRNA is new to you and me, but it is well-known to scientists.
Will the COVID-19 vaccine change my DNA?
mRNA is a messenger in your body. It’s the way your DNA tells the rest of your body what proteins to create for various functions. In your body, mRNA is created in the nucleus of your cells, based on the DNA that resides there. Then the mRNA exits the nucleus to be used as a template for protein-making in the rest of the cell, and it has no way back in. Soon, it degrades without ever re-entering the nucleus or coming in contact with DNA. mRNA lives in the body between a few hours and a couple of days.
Like naturally occurring mRNA that has already left the nucleus of your cells, the mRNA vaccine isn’t able to enter your cell’s nucleus. Because of that process, it can’t come in contact with or change your DNA. Click here to see a video that explains the process more fully.
The Johnson & Johnson vaccine uses a viral vector — a harmless virus-turned-delivery system that’s been used in vaccines before — to introduce the gene that encodes a protein found on the surface of the COVID-19 virus. Our cells then create just this protein (not the whole COVID-19 virus) so our immune systems learn to recognize it. It also will not change your DNA.
Why do I need two shots of the Pfizer or Moderna vaccines?
Multiple doses of the vaccine expose our immune systems to more of the viral proteins, giving it the chance to develop more antibodies and protection. The immunity takes time to develop. Researchers believe that 10 days after the first dose, patients develop about immunity that is 52% effective. About a month after receiving their second dose, immunity can reach 94%. A similar strategy is used for other vaccines, like Shingrix, developed to prevent shingles.
Since the initial assessment, new analysis of the research suggests that two weeks after the injection, a single dose of Pfizer or Moderna’s vaccines is more protective than previously thought, potentially up to 92%.
Will I need a third shot?
Third shots were first authorized for the subset of patients who are immunocompromised due to organ transplants or high doses of corticosteroids. That’s because many of these patients didn’t mount a full-fledged response to the first two shots to begin with, but some studies have shown they respond well to a third. Now, however, as researchers are finding evidence of immunity waning over time, they are recommending third shots for a wider swath of the population, especially those over the age of 65 who are at higher risk, and likely had weaker responses to the first two shots. See the CDC’s guidance on who should get a booster shot here.
How does the FDA decide if a side effect is severe?
The FDA has a toxicity grading scale to rate adverse events related to preventive vaccines. It ranks both local events (like injection site pain) and systemic events (like fever and nausea) as mild (Grade 1), moderate (Grade 2), severe (Grade 3) or life- threatening (Grade 4.) Several effects, like pain at the injection site, headache, fatigue and nausea, are considered Grade 1 if they do not interfere with your activity at all. If side effects do prevent you from doing ordinary tasks, they may be designated Grades 2 or 3. If the symptoms cause you to go to the emergency room for treatment, they are Grade 4.
Is the COVID-19 vaccine safe?
The most common side effects for all three vaccines — headache, fatigue, fever, chills and muscle and joint pain — are more common and intense than those for the flu shot, for example. And the side effects caused by the COVID-19 vaccine tend to be worse after the second shot than the first.
The FDA reported that up to 4.6% of Pfizer vaccine patients, 9.6% of Moderna’s patients, and 2% of Johnson & Johnson’s patients experienced severe (Grade 3) adverse effects. Grade 3 effects are those serious enough to interrupt a person’s life — for example, by causing them to take a day off of work — but not so severe that the person is hospitalized. Younger patients were more likely than older ones to experience severe adverse effects. No life-threatening effects were linked to the Pfizer vaccine and less than 0.1% of patients experience Grade 4 adverse effects to Moderna’s vaccine. Swelling, pain, rashes and redness at the injection site are common.
While some patients have experienced anaphylaxis, all have recovered.
The vaccine will need to be tested on millions of more people for scientists to understand how the vaccine may interact with certain chronic illnesses or other drugs.
Check out MedShadow’s vaccine side-effects tracker for more details and frequent updates on side effects. You can also check out MedShadow’s COVID-19 topic page to find more in-depth reporting on specific findings, like what doctors say about the risk of myocarditis for kids.
How long were test patients followed and why?
The FDA required that patients in the Phase 3 trials be followed for a median of two months after the second shot before the data would be reviewed for its approval.
When it comes to side effects, the CDC considers vaccinations different from other medicines, because they aren’t taken continuously. In general, the CDC designates adverse events that happen within six weeks of administration to be potentially linked to vaccines. In the case of the Pfizer and Moderna vaccines, the mRNA is broken down within days of the injection, so it doesn’t remain in your body long term.
The CDC is tracking possible adverse reactions in early recipients through its V-safe app. The agency initially announced that it would follow these patients for six weeks but has since said it will check in on them at three months, six months and one year after receiving the vaccine. Individuals can also report adverse effects through VAERS, the government’s vaccine adverse event reporting system.
Who has been tested for the vaccine?
The vaccines have been authorized for adults. While Moderna’s and Johnson & Johnson’s vaccines have the okay for patients 18 and older, Pfizer’s original trial included a small number (163) of 16- and 17-year-olds and has been recommended for patients 16 and older. On March 31, the company announced that the vaccine was safe and effective for patients 12-15 years old, and it received emergency use authorization for these patients shortly after. In October 2021, the FDA authorized the Pfizer vaccine for use in children age 5-11. In younger patients, Moderna’s vaccine has been associated with a heightened risk for myocarditis, and regulators are still reviewing data.
The vaccines were effective in both men and women, regardless of weight or race. While Pfizer’s vaccine appears to be just as effective in older patients (65 and older) as in younger ones, Moderna’s vaccine offered slightly less protection (86% compared to 96%) in older patients versus younger ones.
What do we know about how the vaccines work in kids and teens?
Pfizer’s vaccine received Emergency Use Authorization for 12 to 15-year-olds. The company reported that common adverse effects like chills and fever were more common in this age group than adults. Adverse reactions in adolescents 12 through 15 years of age included pain at the injection site (90.5%), fatigue (77.5%), headache (75.5%), chills (49.2%), muscle pain (42.2%), fever (24.3%), joint pain (20.2%), injection site swelling (9.2%), injection site redness (8.6%), lymphadenopathy (0.8%), and nausea (0.4%). These effects generally subsided within 1-2 days. While data on syncope (fainting) was not included, the announcement mentioned that fainting after vaccination is more common in teens than adults, and that safety measures should be in place to reduce this risk.
Moderna announced on May 6 that preliminary data suggest its vaccine is also safe and effective in teens, but has not yet published the data or sought approval. In March the company started a trial in patients as young as 6 months to 11 years old. The trial started with very low doses and will increase them to find the lowest effective dose for children. The children will be followed for a full year.
Is it safe for pregnant women? Will it protect the baby?
None of the initial trials included pregnant or lactating women, but since then, several studies have found positive results. Simultaneously, researchers have found that pregnant patients who contract COVID-19 are at high risk for severe complications, preterm birth, and mortality.
The CDC published an analysis of data on from the first few months of voluntary V-safe surveys on April 22 that suggested that the Moderna and Pfizer vaccines are safe for pregnant women. Pregnant patients self-reported slightly fewer side effects like fever, headache and chills than the general population, but more said they experienced nausea and injection site pain. Rates of adverse pregnancy outcomes such as pre-term birth were similar to rates seen before the pandemic. While promising, officials noted that more studies will be required.
Two more studies published in May found that the vaccine does not damage the placenta and that pregnant women developed sufficient immune responses. Antibodies were passed to their babies through blood and breast milk.
An August 2021 study found the vaccines led to antibodies being transferred to the fetus through cord blood.
A study published in October 2021 in the New England Journal of Medicine found that vaccination was not associated with an increased risk of spontaneous abortion.
Is the vaccine protective for everyone?
Recent studies have suggested that in some patients who take strong immunosuppressants for organ transplants, the vaccine may offer little to no protection. After the second shot, only about half of patients who had received an organ transplant developed sufficient antibody responses. It’s unclear how effective the vaccine will be for other groups who are immunocompromised. Catherine Liu, MD, a vaccine and infectious disease researcher at the Fred Hutchinson Cancer Research Center, suggests this is one reason it’s especially important for healthy people who spend time with patients who have cancer or take immunosuppressants (family members and caregivers, for example) to be vaccinated themselves. A clinical trial is underway to determine if other patients with suppressed immune systems mount a sufficient response to the vaccines.
Will the COVID-19 vaccine protect me from mutated versions of the virus?
Researchers have identified several mutated forms of the virus spreading in the UK, South Africa, Brazil, India and elsewhere. While some variants have been associated with a higher portion of breakthrough infections–infections in people who have been fully vaccinated–these patients usually did not end up seriously ill or hospitalized. So far, the vaccines seem to provide substantial protection from these variants, even if that protection is slightly lower than it is for the original SARS-CoV-2 virus. It’s unclear whether or not we’ll need booster shots to protect against future variants, but vaccine manufacturers are studying them now.
Ok, but what about the Delta and Delta Plus Mutations?
The Delta variant is believed to be far more contagious than previous forms of the virus that causes COVID-19. Researcher have suggested it may be more likely to send you to the hospital as well. So far, scientists say that the Pfizer, Moderna and Astrazeneca vaccines are still likely to protect you from the variant—provided you’ve received both doses and two weeks has passed since that second dose.
While a single dose provided pretty high protection from previous variants, its only generates about 33% efficacy against the Delta variant. After both doses, however, a recent Lancet study suggested that Pfizer’s vaccine is 79% effective against Delta, and Astrazeneca’s is 60%. Protection against hospitalization with Delta was higher, at 96% and 92% for Pfizer and Astrazeneca’s vaccines, respectively. Many studies report different numbers because real-life studies lack the controls of clinical trials, but scientists emphasize that the vaccines do seem to provide protection, especially from hospitalization.
“Their overall implications are consistent: that protection against severe disease remains very high,” said Naor Bar-Zeev, an associate professor at the Johns Hopkins Bloomberg School of Public Health told the New York Times.
Moderna released results of a small lab study that suggests its vaccine is still effective against the variant. Johnson and Johnson also released data from small studies suggesting its vaccine is effective against Delta.
In the meantime, social distancing and face masks can still help protect you against Delta and any other variants.
Can I Throw Away My Masks After I Get the Vaccine?
Initially, the CDC recommended that everyone continue to wear masks after being vaccinated because it was unclear whether you could transmit the disease after vaccination. The initial trials only tested those patients who displayed symptoms, so there’s a chance that you could contract the virus and pass it on without getting sick. Newer, real world data suggests that the vaccines do prevent about most transmission. In Israel, where nearly the entire population is vaccinated, data suggest the vaccines prevent 86% of transmission. A hospital study in the U.S. that tested nearly 4,000 employees weekly regardless of symptoms, demonstrated the vaccines prevented 90% of cases.
On May 13, the CDC announced that fully vaccinated individuals (you are fully vaccinated two weeks after you receive the second dose) could lose their masks in most settings. They’re still recommended in certain circumstances, like when visiting hospitals, nursing homes or jails.
Still, no vaccine is 100% effective and it can be less effective especially in people with weakened immune systems. You’ll want to keep protecting those around you who are elderly, have cancer or other conditions that cause immunodeficiencies. You should continue to follow any local or state guidelines regarding mask wearing. These guidelines could change if larger outbreaks occur.
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