COVID-19 Vaccination

UT Southwestern provides the most recent bivalent Pfizer-BioNTech and Moderna vaccines, which have been created to target the most prominent variants.

The Pfizer and Moderna vaccines use what’s called messenger RNA (mRNA), a synthetic material that carries the genetic code used to make the SARS-CoV-2 spike protein – the part of the virus that attaches to human cells. The mRNA is showing your immune system a part of the virus, so that when your body encounters the whole virus in real-life, it recognizes the invader and is able to mount a quick immune response, activating antibodies (B and T-cells) to fight it.

Vaccines using mRNA are relatively new but the technology has been around for decades and has been used in treatments for other diseases such as cancer and cystic fibrosis. While many vaccines use a weakened or inactive version of the virus to create an immune response, these vaccines don’t so there is no risk of them causing disease.

In fall 2022, the FDA authorized reformulated "bivalent" vaccines from Pfizer-BioNTech and Moderna that target the most prominent variants of the original SARS-CoV-2 virus.

The Pfizer and Moderna vaccines were nearly 95% effective in preventing symptomatic COVID-19 in Phase 3 clinical trials in December 2020, according to the FDA. The protection from the original two-dose primary series wanes over time, which is why booster doses were approved to bring the immune system back to robust levels.

People who have received the primary vaccine series and subsequent boosters are much less likely to experience severe symptoms, hospitalization, or death than people who are not vaccinated against COVID-19.

Vaccines remain the best protection against severe COVID-19 illness and hospitalization. The emergence of variants, such as Delta and Omicron, has only reinforced the importance of getting vaccinated.

The current vaccines have been reformulated to target the most prominent Omicron subvariants.

The vaccines appear to maintain high efficacy rates regardless of age, sex, and ethnicity. For example, Pfizer’s vaccine was 94% effective in adults over age 65, according to safety data. The vaccines have also been tested in people with stable pre-existing conditions such as diabetes and cancer, and efficacy rates held at essentially the same levels.

In April 2023, the CDC recommended that adults 65 and older and those with weakened immune systems receive another booster dose of the reformulated booster that debuted in fall 2022.

It’s unclear how long natural immunity lasts after recovering from COVID-19, so the CDC advises people to get a vaccine even if they have been sick with COVID-19 before.

Vaccinology is one of the safest interventions we have in patient care and disease prevention, and it has a long history of protecting the public – from smallpox to polio to measles.

The COVID-19 vaccines have now been given to hundreds of millions of people around the world, and serious side effects have been extremely rare. There are low-grade side effects, such as arm soreness, fatigue, and fever, but they are minor compared with the protections that a safe and effective COVID-19 vaccine or booster shot can provide.

There is a well-established testing and clinical trial regimen that must be followed for the FDA to consider approving a vaccine. For these COVID-19 vaccines, the research was performed concurrently, rather than consecutively, and the wait times for review of the research were substantially reduced through Operation Warp Speed, a federal program that invested in development and manufacturing of the vaccines.

No steps were skipped, and safety was not sacrificed for speed.

An independent and transparent monitoring board of experts reviewed the trial data, and career scientists evaluated it at the FDA. Clinical trial information has been published in peer-reviewed journals.

Vaccines are typically tested in adults first to ensure they’re safe before pediatric trials begin. While historically, pregnant women have not been included in vaccine trials, a small number of women in the Pfizer clinical trial became pregnant during the study, without any short-term complications.

The Advisory Committee on Immunization Practices and the American College of Obstetricians and Gynecologists have strongly recommended that women who are pregnant, wanting to become pregnant, or breastfeeding receive the COVID-19 vaccines. Studies have shown that the benefits of vaccination for pregnant women and their babies outweigh potential risks and the vaccine can prevent severe illness, death, and pregnancy complications related to COVID-19. Women who have more questions should discuss COVID-19 vaccination with their personal physician.

Severe allergic reactions to vaccines are very rare, even for people who have a history of allergies to food, pets, environmental factors, or oral medications. Still, UT Southwestern is following the CDC’s recommendations and observing patients for 15 minutes in a safe environment after vaccination to monitor for any adverse effects.

Patients who have had a severe allergic reaction to a vaccine, an intravenous medication, or an injectable in the past should discuss COVID-19 vaccination with their provider. In the majority of cases, you can still get the vaccine but with a 30-minute observation period instead.

If you’ve had a severe allergic reaction to one of the components in the COVID-19 vaccines, such as polyethylene glycol or polysorbate, it is recommended that you do NOT get one of the currently available COVID-19 vaccines. Also, if you’ve had a severe or immediate allergic reaction to the first dose of a COVID-19 vaccine, you should NOT get the second dose until you discuss the specifics of the reaction with your provider.

If you are feeling unwell or are having symptoms of COVID-19, please speak with your provider who may recommend that you defer your vaccination until a later date.

There is no evidence or reason to think COVID-19 vaccines affect fertility, despite some claims to the contrary circulating on the internet. Those reports are rooted in the theory that because the SARS-CoV-2 spike protein resembles the syncytin-1 protein, which is crucial for formation of the placenta, the COVID-19 vaccines might prompt an immune response that targets the placenta protein. But virologists say the two proteins are completely unrelated and not similar enough to confuse antibodies that attack the virus.

No. Although these drugs could help with potential side effects, they could also affect your immune response, making the vaccine less effective. It is recommended that you take them after your vaccine only if you are experiencing pain, swelling, or fever.

The most common side effect is soreness at the injection site and headache, with most side effects lasting less than 48 hours.

Clinical trial participants reported arm soreness, fatigue, chills, fever, or headaches that lasted a day or two, most often after the second shot. But that reaction is typically a sign that the vaccine is working – triggering the immune response (or inflammation) indicating your body recognizes this never-before-seen pathogen and is mounting a protective response against it.

The clinical trials will continue to monitor patients for side effects long after patients are vaccinated. The state of Texas will use the Vaccine Adverse Event Reporting System (VAERS), a national system co-managed by the Centers for Disease Control and Prevention (CDC) and FDA, to track vaccine safety and side effects. Texas will also employ an app called V-safe, which sends vaccine recipients text messages and check-in emails to keep tabs on their health, as well as remind them when it’s time to get their second shot.

It is possible to have a delayed reaction or side effect starting more than seven days after your vaccination including fever, body aches, headache, and injection site reactions. Delayed injection site reactions have been reported including pain, swelling, itching, and redness. This is not considered an allergic reaction and does not prevent you from receiving your second vaccination. In addition, these reactions are a positive sign that your immune system is responding to the vaccination. If you have any concerns, please speak with your primary care provider.

Phase three vaccine trial participants were monitored for 60 days after receiving their second shot, which is required before any safety data can be submitted to the FDA. Typically, if a patient hasn’t experienced severe side effects in 60 days, it is extremely unlikely they will. Long-term data are still being collected by the CDC and side effects continue to be monitored.

The FDA documents said the Pfizer vaccine showed 95% immunity seven days after the second shot and the Moderna vaccine showed 94.5% immunity 14 days after the second shot. The full response takes time to develop after the second vaccine, and therefore one is not considered fully vaccinated until two weeks after the second dose.

The booster is necessary to strengthen the immune response and provide full protection. Also, keep in mind that exposure is still possible between doses, so continue to take precautions.

There’s no definitive way to tell yet, but some studies have indicated it could last years, even decades. The research showed that patients who contracted COVID-19 early in 2020 had robust antibodies six months later. Studies of survivors of SARS, also caused by a coronavirus, showed that participants carried immune cells 17 years after being infected. So there are some reasons to be encouraged, but scientists will need to continue monitoring the length and strength of immune responses in vaccinated patients.

No. The vaccines will not influence the results of PCR or antigen COVID-19 tests, as the vaccine does not contain the virus itself – rather it prompts the body to produce antibodies specific for the spike protein. The spike protein is like a key the virus uses to “unlock” and enter our cells. The PCR and antigen tests look for the genetic code of the virus itself, which is not contained in the vaccine, but rather is only present during the viral infection.