Which Vaccine Did You Receive?

Our team all received the Pfizer-BioNTech vaccine. Moderna was recently granted emergency use authorization and will be arriving soon. Both vaccines appear to be equally effective at preventing symptomatic COVID-19. However, since TGH has -80 degree freezers, our institution received the Pfizer-BioNTech vaccine since that one requires a colder storage temperature, limiting distribution locations. Both brands require that you receive 2 doses to achieve optimal immunity. We don’t know at this time if there will be a difference in long-term immunity between the brands. Those choosing to be vaccinated should receive the same brand for both doses. Researchers have not studied how immunity would be affected if one were to be given the alternative vaccine for the 2nd dose. Theoretically, this shouldn’t have much of an impact since both vaccines are mRNA vaccines which ultimately lead to the assembly of the Spike protein.

What are the differences between the two vaccines?

The Pfizer and Moderna vaccines are similar. Below is a table highlighting the two vaccines with Emergency Use Authorization (EUA).

Are there side effects?

Both vaccines were shown to be safe in all testing phases. In the Phase 3 Clinical Trials serious adverse events were very uncommon (<0.5% of patients). The rate of serious adverse events was the same between the experimental group receiving the vaccine and the research participants receiving the placebo. Both vaccines are known to be reactogenic, meaning they may cause some minor symptoms following the vaccine. Common side effects included things like pain at the site of injection, fatigue, muscle pain, headaches, and some participants have experienced fever. These minor side effects should not be equated to the vaccine being bad. These symptoms can be expected as the body forms an immune response. These symptoms occurred more frequently after the 2nd dose and were seen more frequently in younger participants (likely secondary to a more robust immune response). I personally experienced shoulder pain on day one. On post-vaccine days 2 and 3, I felt tired and a bit achy all over, so I happily laid around on the couch. I am now on day 4 and feel completely normal. Most people report resolution of their post-vaccine symptoms within 1-2 days. In the Pfizer vaccine group, there were 4 reported cases of Bell’s Palsy. However, this number reflects what we would expect to see within the general population, so it is impossible to say this was secondary to the drug. This is something we will continue to monitor. To date, there have been 3 serious allergic reactions to Pfizer since EUA administration of the vaccine. 2 out of the 3 patients had a history of prior allergies. If you have had a serious reaction to a vaccine in the past, you should discuss this with your physician prior to obtaining the vaccine. Side effects will continue to be closely monitored and reported.

Was the vaccine rushed? How do we really know it is safe?

It’s incredible how quickly scientists were able to develop this vaccine. Some have compared this vaccine accomplishment to astronauts landing on the moon. The speed of production definitely made me take pause and dig a little deeper into how exactly this was possible. Upon digging, I found the vaccine to be safe and effective. Several factors contributed to this astonishing feat. The entire world was desperately searching for a cure. The medical and scientific community has worked day and night since the beginning of the pandemic. Luckily, corona viruses have been studied before and researchers were familiar with similar strands of the virus such as those that caused SARS & MERS. This gave researchers a bit of a head start in the process. In addition, researchers have spent over a decade working on the development of mRNA vaccines for other diseases such as rabies, so the idea of creating an mRNA vaccine was not a completely new concept either. The COVID-19 vaccine is the first commercially available mRNA vaccine but it is not the first mRNA vaccine to ever be developed. There are two basic challenges in bringing a new vaccine to market: Challenge 1 - develop a vaccine, Challenge 2 - test the vaccine and prove it is safe and effective. Challenge 2 is no easy process. Testing new drugs and vaccines is a lengthy and expensive process which can be more time consuming than the developmental phase of the product.

Testing of vaccines (or any new drug for that matter) begins with making sure it appears safe, sometimes using animals, as researchers go through three phases of clinical trials prior to seeking approval of the drug by the FDA. The traditional method of progression can take years for each phase to be complete. With each progressive phase, larger numbers of study participants are included and this is done in a sequential fashion. For example, in Phase 1 researchers give the vaccine to a small number of humans and look for any side effects or safety concerns. Phase 1 generally includes around 20-100 participants and the duration of this phase usually takes several months to complete. Phase 2 continues to evaluate the safety of the vaccine but studies are designed to further determine what dosage is effective. In Phase 2 more patients are enrolled (usually several hundred participants) and completion of Phase 2 can take up to 2 years on average. In Phase 3, researchers compare the drug to an existing treatment option or placebo to determine if the drug is effective. Safety of the drug continues to be investigated. This process can involve thousands of patients and take years to complete. If the drug is found to be safe and effective after completion of Phase 3 the FDA may approve the drug for use. Even after approval, data regarding side effects is continued to be studied.

The COVID-19 mRNA vaccines have been through all 3 Phases of Clinical Trials and included thousands of patients (more than 40,000 in the Pfizer Trials and over 30,000 in the Moderna trial - note that half of these patients actually received the vaccine) but things were done at a much more rapid pace. Researchers were able to do this secondary to enormous amounts of funding and by overlapping the 3 Phases to shorten the overall duration. It is important to realize that although this process was fast, the vaccines were proven to be safe prior to the release of the vaccine for EUA.

After reviewing the data, I can assure you that even healthy people are at a much higher risk of developing complications from COVID-19 than they are from developing complications from the vaccine. The decision to become vaccinated is about weighing the risks and benefits and when you look at the data, there is no question that nearly all people should opt for the vaccine. With every day that passes the medical and scientific community is learning more about COVID-19. The amount of knowledge we’ve gained is immense and there is still so much left to learn. As new knowledge comes it guides our recommendations and management. We’ve all witnessed this throughout the pandemic and though at times it can be confusing and imperfect, every step along the way we must continually assess the risks and benefits. I am thrilled that we have a highly effective and safe vaccine available. We may find even better options to prevent and treat the disease as time goes on. I’ll continue to keep my commitment as a physician and researcher to keep digging. I choose to stand with science rather than making Covid-19 about fear mongering or politics. Know the Facts.

The above figure demonstrates a clear reduction in cases of Covid-19 following vaccination. The title of the graph chosen by the authors, "Efficacy of BNT162b2 against Covid-19 after the First Dose," is not meant to imply that participants received only one dose of the vaccine but rather references time point 0 as time of the first vaccine administration. Though the second dose is not documented on the graph (it occurred on day 21), all participants in this cohort received both doses of the vaccine. The graph begins to diverge on day 12 following the vaccine. The efficacy of the vaccine was found to be 52% when measured between the administration of dose one and dose 2 (this approximates the effectiveness of the vaccine if we were to get 1 administration of the vaccine) and 95% effective at preventing symptomatic Covid-19 after participants received both doses of the vaccine when measured at least 7 days following dose 2. 95% is an impressive number for vaccine efficacy and this explains why we must receive 2 doses of the current Pfizer vaccine. Similar results were seen with the Moderna vaccine.

Important Limitations

The vaccine studies we have to date do NOT answer whether vaccination prevents asymptomatic infection. There’s a good chance that the vaccine does decrease overall asymptomatic infection but we can’t say for sure yet because participants were tested upon developing symptoms. It’s possible that vaccinated people may still transmit the virus (fingers crossed this chance is low). This is why we should keep wearing the masks.

The obvious limitation we have is a lack of long-term safety data. Ongoing data is still being collected. The risks of doing nothing are exceedingly high and will certainly result in many preventable deaths. This is why I urge you to get vaccinated.

Since we don’t have long-term data yet, we don’t know how long immunity will last. Participants still had protection against Covid-19 at the 2 month mark. We may find that we require additional administration of the vaccine to keep immunity.

We don’t have vaccine data on children yet.

Many of you have asked me about receiving the vaccine in pregnancy. Please discuss this with your physician. The vaccine trials excluded pregnant women. However, 23 women in the Pfizer-BioNTech trial and 13 in Moderna's became pregnant during the trial. This is a tiny number! Pregnant women do appear to be at higher risk for severe covid, especially if they have underlying diabetes, obesity, or hypertension. The benefits of the mRNA vaccine likely outweigh the risks. Fever is one potential side effect of the vaccine that may be harmful to the fetus. Odds of experiencing severe complications with Covid-19 are felt to be much higher. I wish we had an answer! The Society for Maternal-Fetal medicine strongly recommends that pregnant individuals have access to Covid-19 vaccines. The American College of Obstetricians and Gynecologists recommends that Covid-19 vaccine should not be withheld from pregnant individuals who meet criteria for vaccination. Here’s one resource for pregnant women developed by Baystate Health/University of Massachusetts Medical School that I found helpful: https://rebelem.com/wp-content/uploads/2020/12/Vaccine-Info-for-Pregnant-Women.pdf.

References

Moderna announces primary efficacy analysis. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-primary-efficacy-analysis-phase-3-cove-study. Published November 30, 2020.

https://www.fda.gov/media/144245/download

Ives-Tallman Crystal, Guest Britt. Novel Coronavirus 2019 (COVID-19). In: Mattu A and Swadron S, ed. CorePendium. Burbank, CA: CorePendium, LLC. https://www.emrap.org/corependium/chapter/rec906m1mD6SRH9np/Novel-Coronavirus-2019-COVID-19#h.70vvhip0ljks. Updated December 9, 2020. Accessed December 20, 2020.

https://www.fda.gov/media/144412/download

https://www.pfizer.com/science/clinical-trials/guide-to-clinical-trials/phases

Alberer M, Gnad-Vogt U, Hong HS, Mehr KT, Backert L, Finak G, Gottardo R, Bica MA, Garofano A, Koch SD, Fotin-Mleczek M, Hoerr I, Clemens R, von Sonnenburg F. Safety and immunogenicity of a mRNA rabies vaccine in healthy adults: an open-label, non-randomised, prospective, first-in-human phase 1 clinical trial. Lancet. 2017 Sep 23;390(10101):1511-1520. doi: 10.1016/S0140-6736(17)31665-3. Epub 2017 Jul 25. PMID: 28754494.

Ball, Philip. The Lightning Fast Quest for COVID Vaccines - and What it Means for Other Diseases. Nature. Retrieved from https://www.nature.com/articles/d41586-020-03626-1.

Polack FP et al. Safety and Efficacy of the BNT162b2 mRNA COVID-19 Vaccine. NEJM 2020. PMID: 33301246

Frank Lodeserto MD, "COVID-19 Update: The COVID-19 Pfizer Vaccine", REBEL EM blog, December 15, 2020. Available at: https://rebelem.com/covid-19-update-the-covid-19-pfizer-vaccine/.

Ellington S, Strid P, Tong VT, et al. Characteristics of Women of Reproductive Age with Laboratory-Confirmed SARS-CoV-2 Infection by Pregnancy Status - United States, January 22-June 7, 2020. MMWR Morb Mortal Wkly Rep. 2020;69(25):769-775. Published 2020 Jun 26. doi:10.15585/mmwr.mm6925a1.

Allotey J, Stallings E, Bonet M, et al. Clinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and meta-analysis. BMJ. 2020;370:m3320. Published 2020 Sep 1. doi:10.1136/bmj.m3320

About the author

Dr. Okonkwo is the Assistant Program Director at USF Emergency Medicine. She is an emergency physician who also conducts clinical research. She is currently involved in Covid-19 research at Tampa General Hospital.

Post edited by Dr. Jason Wilson