The rapid development and administration of the COVID-19 vaccine have been a cause of concern for patients, the general public, administrators, and clinicians alike. Many of the concerns of healthcare professionals overlap with the concerns of those in the general public. While research is ongoing, the following reflects up-to-date information around the vaccination.

See here for a Vaccine Comparison Chart with Frequently Asked Questions about the Pfizer, Moderna, Johnson & Johnson, Novavax, and AstraZeneca vaccines.

Clinicians and Administrators

mRNA vaccines have been studied for more than a decade (Maruggi et al., 2019). mRNA vaccines have the capacity to overcome novel vaccine compositions and overcome many of the mass manufacturing barriers faced currently (Jackson et al., 2020). Because of the attention to mRNA research in the past number of years, COVID-19 researchers were not starting from scratch.

mRNA is non-infectious and clinical trials have shown no risk of infection or insertional mutagenesis. In other words, there is no risk of creation of mutations of DNA due to artificial mRNA (Pardi et al., 2018). mRNA is degraded and excreted by natural, normal cellular processes (Pardi et al., 2018). mRNA’s ability to induce the body’s immune reaction (immunogenicity) can be manipulated to enhance safety (Kariko et al., 2008; Thess et al., 2015). Studies have shown promise that mRNA vaccines will demonstrate ideal qualities of a vaccine. In particular, mRNA vaccines have shown safe outcomes in animals and are adaptable for rapid application to new infectious diseases (Pardi et al., 2018; Petsch et al., 2012; Bahl et al., 2017).

mRNA vaccines have been studied previously in cancer settings, and have shown promising results in prolonged disease-free survival in many cases (Pardi et al., 2018). Other cases of mRNA elicited potent immunity to infectious diseases include its efficacy in Zika, rabies, and influenza (Alberer et al., 2017; Van Driessche et al., 2009; Pardi et al., 2018). See here for a table of mRNA vaccine strategies that have been developed and here for a list of clinical trials employing mRNA vaccines against infectious diseases.

Additionally, the short manufacturing time inherent in mRNA production is advantageous to avoid contamination with other viruses, a concern presented in the production of other vaccines (Pardi et al., 2018).

In addition to the extensive investigation into mRNA vaccine safety over the last few years, the global collaboration from experts in the field lends credibility to the vaccine’s safety. Regulatory experts from around the world were convened in a WHO forum to review the data around the Pfizer/BioNTech vaccine, a key part of the risk-versus-benefit analysis (WHO, 2020). Additionally, the U.S.’s Operation Warp Speed accelerated the development of the vaccine by facilitating public and private partnerships with more than a dozen leading biopharmaceutical companies and national and international organizations, such as the CDC, FDA, and the European Medicines Agency (EMA) (National Institutes of Heatlh, 2020). 

In a review of the safety and efficacy of the mRNA COVID-19 vaccine, study participants underwent randomization in which 43,448 participants received the vaccine. The study determined that a two-dose regimen of “BNT162b2 conferred 95% protection against COVID-19 in persons 16 years of age or older.” The safety of a 2-month period was similar (or comparable) to other viral vaccines (Polack et al., 2020). The rushed timeline did NOT compromise the accuracy of the vaccines. In fact, the influenza vaccine is only 40-60% effective in preventing the influenza virus (CDC, 2019).

Although data suggests that receiving the vaccine is safe, it is also important to note some adverse reactions may occur as a result of receiving a dose of the vaccine. There have been reports of severe allergic reactions (anaphylaxis) from receiving the vaccine. Those who have a history of severe allergic reactions to the ingredients in the vaccine should speak with their doctor (CDC, 2020).


General Public, Patients, and Family Members

For both vaccines, the laboratory-made mRNA within the vaccine is blanketed in a fatty layer, which serves to protect against the immune system when the vaccine is administered. Once the vaccine is inside a cell, the cell makes one of several proteins of SARS-CoV-2.

Then, the immune system will respond to that protein and produce antibodies, without actually having been infected with the COVID-causing virus itself. Therefore, if the person does come into contact with SARS-CoV-2  virus in their community, they already have the antibodies ready to neutralize the virus when it is in smaller quantity. The first dose helps the immune system create a response against SARS-CoV-2, the virus that causes COVID-19. The second dose further boosts the immune response for longer term protection.

Understanding how COVID-19 vaccines work
Understanding COVID-19 mRNA vaccines

Clinicians and Administrators

SARS-CoV-2, the virus that causes COVID-19, contains four structural proteins, that include spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins. However, both Pfizer and Moderna vaccines only contain synthetically made coronavirus spike gene.

The spike protein of SARS-CoV-2, comprised of S1 and S2 subunits, is involved in binding to the host cell-surface receptor during host cell entry. The spike portion of the virus is recognized by the host immune system, which then produced antibodies in response. Both the Pfizer and the Moderna vaccines synthesize the portion of the RNA that codes for the spike gene, mix it with an artificial lipid, and this mixture is then injected into the muscle. When this vesicle is introduced into the cell, the body will produce the spike protein, which will initiate an immune response by producing neutralizing antibodies. Thereafter, upon further encounters with the virus itself, the antibodies produced will be able to bind around the virus and neutralize it.

See a Pfizer and Moderna vaccine comparison chart here.


General Public, Patients, and Family Members

Both the Pfizer and Moderna vaccines are authorized and recommended to prevent COVID-19 (CDC, 2021).


  • 2 shots, 21 days apart
  • Recommended for those 16 years old and older
  • 95% effective at preventing COVID-19 in those without a previous COVID-19 infection
  • Common side effects include pain, swelling, and redness at the site of injection and chills and tiredness throughout the body
  • Typically, side effects start 1-2 days after receiving the vaccine.

See CDC (2021) for further information about the Pfizer vaccine.


  • 2 shots, 28 days apart
  • Recommended for those 18 years old and older
  • 94.1% effective at preventing COVID-19 in those without a previous COVID-19 infection
  • Common side effects include pain, swelling, and redness at the site of injection and chills, tiredness, and headache throughout the body
  • Typically, side effects start within 1-2 days after receiving the vaccine

See CDC (2021) for further information about the Moderna vaccine.

There have been reports of severe allergic reactions from receiving both vaccines. Symptoms often occur within 15-30 minutes of vaccination, though it can sometimes take several hours for symptoms to appear.

What to expect after getting a COVID-19 vaccine

Other companies, such as Johnson & Johnson, AstraZeneca, Sanofi, and Novavax, are introducing new vaccines to market soon that may be more appropriate for the global vaccination campaign.

The Johnson & Johnson vaccine, which requires storage at 35.6 to 46.4 degrees F, completed its phase III clinical trial of a single dose vaccination, which demonstrated efficacy and safety of the vaccine 14 and 28 days after receiving the vaccine (Johnson & Johnson, 2021).

The AstraZeneca vaccine, which requires storage at 36-46 degrees F, was recommended for use in the European Union on January 29, 2021 (AstraZeneca, 2021).

Sanofi is exploring two vaccine candidates, one a recombinant protein vaccine and one a mRNA vaccine, in hopes of delivering the best possible global solution based on need (Sanofi, 2021).

The Novavax vaccine was the first to demonstrate efficacy against the UK and South African COVID-19 variants. At the conclusion of its Phase III UK clinical trial, this vaccine showed an 89.3% effectiveness (Novavax, 2021).

The Sputnik V vaccine, the first registered vaccine against COVID-19, has been imported into countries like Mexico in mass quantities (Reuters, 2021).

The Pfizer and Moderna vaccines perform similarly. The Pfizer vaccine is 95% effective, which is similar to the best vaccines we have. The Moderna vaccine has 94.1% effectiveness.

It is not possible to develop COVID-19 illness from the vaccine. The vaccine only contains a portion of the SARS-CoV-2 gene. It does not contain the complete blueprint of the genetic material of the virus. It has instructions to produce only the spike protein. Since instructions to produce the other 3 structural proteins are missing, there is no way to create the SARS-CoV-2 virus protein from incomplete RNA instructions.

For both the Pfizer and Moderna COVID-19 mRNA vaccines specifically, the RNA does not go into the nucleus so it doesn’t interact with human DNA. Humans do not have enzymes to make DNA from RNA, so there isn’t a way to produce DNA from these RNA vaccines.

It is recommended to get the vaccine, even if you have had COVID-19 because it is unknown how long the body’s protective mechanisms will last and it is suggested that the artificial vaccine may provide a more robust immune response than being infected with the virus naturally.

Those who are under 16 years old should not get the Pfizer vaccination and those who are under 18 years old should not get the Moderna vaccination because emergency use authorization has not been granted for testing within these populations for their respective vaccines. Those who have a known allergy to an ingredient within the virus should not get the vaccine. Neither the Pfizer nor the Moderna vaccine contains egg, preservatives, or latex.

According to the American College of Obstetrics and Gynecology, the vaccine should not be withheld from pregnant or lactating women. Pregnant or soon to be pregnant women may benefit from discussion with their healthcare professional, but it is not mandatory before administration of the vaccine.

The mRNA vaccines do not have the live virus within, genetic material does not enter the nucleus, and it does not change the host’s human DNA. Therefore, the mRNA vaccines cannot cause any genetic changes. Therefore, there is no risk of vaccine-induced infection. Immunocompromised individuals may still receive the vaccine (CDC, 2021).

It has been shown that even those ages 18-49, without underlying medical conditions, have faced severe illness, hospitalization, and death. In addition to the direct effects that can manifest without the vaccine, those who are low risk should still receive the vaccination to enhance herd immunity.

Those conducting phase 3 vaccine research are still determining whether vaccinated individuals can still transmit the virus and to what extent. It takes two weeks to build immunity after the second dose, and during that period, vaccinated people can get infected and can infect others. It is likely that vaccinated individuals are less likely to transmit the virus but further research is needed (Johns Hopkins, 2021; FDA, 2020; FDA, 2020).

Be sure to track your symptoms after receiving the vaccination. For example, the CDC provides a smartphone tracking mechanism called “V-Safe”.

Those vaccinated should take the same precautions, which include social distancing, wearing a mask, and washing hands frequently. The vaccine provides only 50% protection after 14 days and 95% protection after the second dose. Therefore, an individual is never 100% protected. Additionally, it is unknown how long the protection from the vaccine lasts. Finally, some individuals may be unable to receive the vaccine for various health reasons and will remain at risk until herd immunity is achieved (FDA, 2020; FDA, 2020).

Clinicians and Administrators

Since November 2020, a variant of SARS-CoV-2 has become prevalent in southeast England, accounting for 60% of recent infections in London. The variant is called “SARS-CoV-2 VOC 202012/01”.

Mutants are particularly concerning for vaccination efforts, as there is the potential for the mutant to evade vaccine-induced immunity and, therefore, become an ‘escape mutant’. However, according to the CDC, early reports have found very little evidence that variants have any impact on the vaccine efficacy (CDC, 2021).

Viruses have only been sequenced in 51,000 of the 17 million US cases and therefore, there could very well be additional mutants that we haven’t discovered yet. While the UK-specific mutant has not been detected in the US, again, it just may not be detected due to the lack of sequencing of all US cases (CDC, 2020).


General Public, Patients, and Family Members

If there are different ‘types’ of the COVID-19-causing virus, the vaccines currently being developed may be inadequate to protect against all of these variants. However, experts agree this isn’t likely due to lack of evidence.