Timeline of the two mRNA COVID-19 vaccines

Dec 10: Vaccine and Biological Products Advisory Committee (VRBPAC) voted to recommend FDA emergency use authorization (EUA) of the Pfizer-BioNTech Vaccine for the prevention of COVID-19 in persons aged 16 or older

Dec 11: FDA issued (emergency use authorization) EUA for the Pfizer-BioNTech Vaccine in persons aged 16 years or older

Dec 12: Advisory Committee on Immunization practices (AICP) meeting to discuss recommendations for its use

Dec 17: VRBPAC meeting to discuss emergency use authorization of the Moderna COVID-19 vaccine for the prevention of COVID-19 in individuals 18 years or older

Dec 18: FDA issued EUA for the Moderna Vaccine in persons aged 18 years or older

ACIP recommends that 

1) health care personnel

2) residents of long-term care facilities

Be offered vaccination in the initial phase of the COVID-19 vaccination program (phase 1A)

ACIP will consider next prioritization groups (phase 1B and 1C) on Dec 20, 2020


1) Both products demonstrate vaccine effectiveness >90%

Protection from vaccine is not immediate and the 2-dose series will take 1-2 weeks following the second dose to be considered fully vaccinated.

 2) Side effects

Pfizer-BioNTech (less reported than with Moderna)

Fatigue 3.8%

Headache 2%

High fever 39-40C ( 102F) <2%


Fatigue almost 10%

Muscle pain 9%

Joint pain 5%

Headache 4.5%

High fever < 2%

Reactogenicity greater in younger people and more after the second dose.

3) Co-administration or temporal administration of other vaccines?

No delay in vaccines recommended but other vaccines should be spaced 14 days before or after COVID-19 vaccine.

4) Duration between first and second dose?

Grace period +/- 4 days before or after

If 2 nd dose falls outside this grace period i.e. day 25, there is no recommendation to restart the series, i.e. no need for 3 doses

If someone develop COVID-19 between the first and second dose of the vaccine, they should wait to get the second dose till able to meet criteria to discontinue isolation for COVID-19

5)When to vaccinate if you have had COVID -19?

When not symptomatic with a febrile illness and out of the isolation period for active disease per CDC guidelines

If documented COVID-19 within 90 days consideration may be given to defer vaccine since reinfection with SAR-COV-2 is uncommon within 90days

No antibody test recommended prior to the COVID-19 vaccine

6) Mixing of the Pfizer/Moderna regimens?

Not recommended but if mixing occurs no recommendation to resume series

7)Recipient of Monoclonal antibody therapy?

Defer COVID-19 vaccine for 90 days

8) Immuno-compromised persons?

Stable HIV. HBV,HCV were not excluded from the vaccine trials.

But other immune-compromised groups were not included in data. However, these patients are at risk for more severe disease. So the recommendations favor vaccination as in non-live vaccines. 

9) Pregnancy?

COVID-19 vaccine is not a live vaccine. Both EUA and package insert do not list pregnancy as a contraindication.

Observational data demonstrate that pregnant people have more severe illness like ICU admission and mechanical ventilation and adverse pregnancy outcomes like premature births.

10) Lactation?

No evidence that mRNA is excreted in breast milk so no prohibition in lactation

11) Anaphylaxis?

Don’t vaccine in persons with anaphylaxis to any component of the vaccine.

Polyethylene glycol is a big one – found in MiraLAX and bowel preps for example. 

People with food, nuts, latex, animal allergies are not an exclusion to get this vaccine.

For people with a prior anaphylactic reaction in past should have a 30-minute observation period post vaccination. 

12) Any effect of vaccine on diagnostics?

There is no evidence that the vaccine will effect the PCR testing.

13) Antibody testing?

How to distinguish antibodies from infection verses vaccine.

Spike protein antibody – vaccine immunity

Nucleic capsid antibody – natural immunity

14) Continue Adherence to PPE use, social distancing guidelines, quarantine guidelines after exposure

15) Premedication prior to vaccination?

No recommendation to pre-emptively take premedication. 

If symptoms occur take medication for symptom control OTC.

NSAID are not worse than acetaminophen.

In pregnancy prefer acetaminophen. 

16) Will vaccine prevent asymptomatic spread of SARS-Cov-2

We don’t have data to validate this supposition. 

This is an important question since 30-40% infections are asymptomatic.

The Pfizer and Moderna trials are not designed to address this question.

These vaccines prevent disease but we don’t know about transmission. 

AstraZeneca trial may have a subset that may answer this question.

17) mRNA platform – myths surrounding this?

mRNA can integrate into the human genome?

The vaccine contains lipid nano particles that encapsulate the mRNA that codes for the spike protein along with stabilizers – it contains no preservatives.

Once administered this is taken up by human cells  the lipid vehicle release the mRNA onto the cytosol of the cell –> RNA is very labile  within the cell it does not enter the nucleus at all (transcription occurs from DNA to RNA in the cell and not vice versa) –-> the code carried for the Spike protein is translated into the Spike protein –> this is seen by the immune system and therefore generates the immune responses which are TH1 and antibody responses as well as T cell responses The mRNA is destroyed once it transcribes into Spike proteinImmune response is generated with in 14 days.

There is no reverse engineering of RNA into DNA. 

This is neither a live or attenuated vaccine – it is a different platform – an amazing bit of technology. 

18) Adverse reaction monitoring platforms

VARES – vaccine adverse reaction monitoring system – passive reporting by providers

VSAFE – patients regularly report symptoms – voluntary enrollment by vaccine recipients – 2 weeks of text message reminders – then 3 months 6 months then a year to pick up signals of increase adverse effects

It will be in English and Spanish

19) for more in-depth information : https://www.fda.gov/media/144583/download