Information about Pfizer's covid-19 vaccine. Includes facts about the mRNA vaccine, the study results, safety, efficacy, and other considerations

1. Covid-19 Pandemic:
Pfizer’s SARS-CoV-2 Vaccine
Announcement
Rachel Mackelprang, Ph.D.
California State University Northridge
Department of Biology
rachel.mackelprang@csun.edu
@rmackelprang

2. First results from any late-stage vaccine trial: take homes
On November 9th 2020, Pfizer and German partner BioNtech announced results
from a combined Phase II/III vaccine trial
Data suggests the vaccine may be more than 90% effective
So far, it appears to be safe. No serious safety concerns have been reported.
30 to 40 million doses could be produced by the end of 2020 and 1.3 billion does in a
year. This still falls well short of the globe’s population of 7.8 billion
Pfizer did not receive money from the US government to develop the vaccine. They have
an advance purchase agreement, meaning the the government will pay Pfizer for the
vaccines upon delivery.

3. Stages of vaccine development
Exploratory Preclinical Phase I Phase II Phase III Approval Surveillance
Safety &
dosage
testing
Expanded
safety trials
Large-scale
efficacy
tests
Approved
for limited
use
Animal trials
Results announced November 9th are from a combined Phase II/III study
Typically these phases are separate, but were combined to accelerate development.

4. Stages of vaccine development
Exploratory Preclinical Phase I Phase II Phase III Approval Surveillance
Safety &
dosage
testing
Expanded
safety trials
Large-scale
efficacy
tests
Approved
for limited
use
Animal trials
Results announced November 9th are from a combined Phase II/III study
Typically these phases are separate, but were combined to accelerate development.
The vaccine was given to tens of thousands of people to determine:
• Whether the vaccine acts differently in different groups (e.g., children, middle aged, elderly)
• Vaccine safety
• Ability to stimulate the immune system
• Whether the vaccine protects against SARS-CoV-2

5. Study overview
43,538 volunteers from
the US, Argentina, Brazil,
and Germany

6. Study overview
43,538 volunteers from
the US, Argentina, Brazil,
and Germany Placebo
Dose 1
Divide subjects into groups: those who
receive the vaccine and those who receive
a placebo

7. Study overview
43,538 volunteers from
the US, Argentina, Brazil,
and Germany Placebo
Dose 1
Divide subjects into groups: those who
receive the vaccine and those who receive
a placebo
Dose 2
Volunteers receive a 2nd dose
or a placebo 21 days after the
initial dose
Placebo

8. Study overview
43,538 volunteers from
the US, Argentina, Brazil,
and Germany Placebo
Dose 1
Divide subjects into groups: those who
receive the vaccine and those who receive
a placebo
Dose 2
Volunteers receive a 2nd dose
or a placebo 21 days after the
initial dose
Placebo
This is a double-blind trial: Neither the volunteer or person administering the injection knows who
receives the vaccine or placebo

9. Study overview
43,538 volunteers from
the US, Argentina, Brazil,
and Germany Placebo
Dose 1
Divide subjects into groups: those who
receive the vaccine and those who receive
a placebo
Dose 2
Volunteers receive a 2nd dose
or a placebo 21 days after the
initial dose
Placebo
Dose 2
Dose 1
Track COVID-19 cases 7 days or more after 2nd dose
This is a double-blind trial: Neither the volunteer or person administering the injection knows who
receives the vaccine or placebo

10. Study results
Do volunteers who received the vaccine become infected at a lower rate than those who
received the placebo?

11. Study results
Do volunteers who received the vaccine become infected at a lower rate than those who
received the placebo?
As of November 9th, 95 volunteers contracted COVID-19. The vaccine was reported to have an efficacy rate of
>90%. This means suggests that more than 85 of the 95 cases were from the placebo group.

12. Study results
Do volunteers who received the vaccine become infected at a lower rate than those who
received the placebo?
43,538 volunteers from
the US, Argentina, Brazil,
and Germany Placebo
Dose 1 Dose 2
Placebo
As of November 9th, 95 volunteers contracted COVID-19. The vaccine was reported to have an efficacy rate of
>90%. This means suggests that more than 85 of the 95 cases were from the placebo group.
More than 85 cases are from the placebo
group
Fewer than 10 cases from the vaccinated
group

13. Side effects: is it safe?
Side effect data from phase I trial (which tested safety and immune response but not efficacy)
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM

14. Side effects: is it safe?
Side effect data from phase I trial (which tested safety and immune response but not efficacy)
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM
Three dose levels and placebo
10 µg 20 µg 30 µg Placebo

15. Side effects: is it safe?
Side effect data from phase I trial (which tested safety and immune response but not efficacy)
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM
Measured*
🤒 🥱 🥶
Fever Fatigue Chills
Three dose levels and placebo
10 µg 20 µg 30 µg Placebo
Other side effects were also evaluated. See
paper for further details*

16. Side effects: is it safe?
Side effect data from phase I trial (which tested safety and immune response but not efficacy)
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM
Measured*
🤒 🥱 🥶
Fever Fatigue Chills
Three dose levels and placebo
10 µg 20 µg 30 µg Placebo
Mild: Did not interfere with daily activity
Moderate: Some interference with daily activity
Severe: Prevented daily activity
Grade 4: Required hospital visit. This level was
not observed
Evaluated severity of side effects
Other side effects were also evaluated. See
paper for further details*

17. Side effects: is it safe?
Side effects were similar to other vaccines (e.g. flu) and increased with dose
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM

18. Side effects: is it safe?
Side effects were similar to other vaccines (e.g. flu) and increased with dose
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM
🤒 🥱 🥶

19. Side effects: is it safe?
Side effects were similar to other vaccines (e.g. flu) and increased with dose
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM
🤒 🥱 🥶
Other side effects (e.g. pain at injection
site, headache, muscle pain, vomiting)
were similar or less severe. See link at
bottom of slide to access all data.

20. Side effects: is it safe?
Side effects were similar to other vaccines (e.g. flu) and increased with dose
Side effect info from phase I trial: https://www.nejm.org/doi/10.1056/NEJMoa2027906
Walsh et al. 2020. NEJM
🤒 🥱 🥶
Note: when evaluating side effects,
take into consideration the symptoms
reported by the placebo group.
Especially for fatigue.
Other side effects (e.g. pain at injection
site, headache, muscle pain, vomiting)
were similar or less severe. See link at
bottom of slide to access all data.

21. How does the vaccine work?
The SARS-CoV-2 genome
contains instructions in the form
of RNA to make all the different
part of the virus

22. How does the vaccine work?
The SARS-CoV-2 genome
contains instructions in the form
of RNA to make all the different
part of the virus
The vaccine uses the RNA sequence
that contains instructions on how to
make the spike protein
Spike protein RNA instructions
for making the
spike protein

23. How does the vaccine work?
The SARS-CoV-2 genome
contains instructions in the form
of RNA to make all the different
part of the virus
The vaccine uses the RNA sequence
that contains instructions on how to
make the spike protein
Spike protein RNA instructions
for making the
spike protein
The vaccine encapsulates
spike protein RNA
instructions inside a lipid
coat

24. How does the vaccine work?
The SARS-CoV-2 genome
contains instructions in the form
of RNA to make all the different
part of the virus
The vaccine uses the RNA sequence
that contains instructions on how to
make the spike protein
Spike protein RNA instructions
for making the
spike protein
The vaccine encapsulates
spike protein RNA
instructions inside a lipid
coat
Our cell membranes merge with the lipid coat,
releasing the RNA into the cell

25. How does the vaccine work?
The SARS-CoV-2 genome
contains instructions in the form
of RNA to make all the different
part of the virus
The vaccine uses the RNA sequence
that contains instructions on how to
make the spike protein
Spike protein RNA instructions
for making the
spike protein
The vaccine encapsulates
spike protein RNA
instructions inside a lipid
coat
Our cell membranes merge with the lipid coat,
releasing the RNA into the cell
Our cells’ molecular machines (called
ribosomes) translate the RNA instructions
into spike proteins

26. How we develop immunity during infection
Virus is ingested by
specialized immune
system cells called
‘antigen presenting
cells’
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html

27. How we develop immunity during infection
Virus is ingested by
specialized immune
system cells called
‘antigen presenting
cells’
T-helper cell
Antigen presenting cells
display pieces of the virus to
activate T-helper cells
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html

28. How we develop immunity during infection
Virus is ingested by
specialized immune
system cells called
‘antigen presenting
cells’
T-helper cell
Antigen presenting cells
display pieces of the virus to
activate T-helper cells
T-cells activate other
immune responses
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html

29. How we develop immunity during infection
Virus is ingested by
specialized immune
system cells called
‘antigen presenting
cells’
T-helper cell
Antigen presenting cells
display pieces of the virus to
activate T-helper cells
Cytotoxic
T-cell
Cytotoxic T-cells identify
and destroy virus-
infected cells
T-cells activate other
immune responses
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html

30. How we develop immunity during infection
Virus is ingested by
specialized immune
system cells called
‘antigen presenting
cells’
T-helper cell
Antigen presenting cells
display pieces of the virus to
activate T-helper cells
Cytotoxic
T-cell
Cytotoxic T-cells identify
and destroy virus-
infected cells
B-cell
B-cells make antibodies that block the virus from
infecting more cells and mark it for destruction
T-cells activate other
immune responses
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html

31. How we develop immunity during infection
Virus is ingested by
specialized immune
system cells called
‘antigen presenting
cells’
T-helper cell
Antigen presenting cells
display pieces of the virus to
activate T-helper cells
Cytotoxic
T-cell
Cytotoxic T-cells identify
and destroy virus-
infected cells
Long-lived ‘memory’ B and T cells that
recognize the virus patrol the body for
months or years, providing immunity
B-cell
B-cells make antibodies that block the virus from
infecting more cells and mark it for destruction
T-cells activate other
immune responses
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html

32. Vaccines allow us to mount a rapid immune response
T-helper cell
Antigen presenting cells
display spike proteins to
activate T-helper cells
Cytotoxic
T-cell
Cytotoxic T-cells identify
and destroy virus-
infected cells
Long-lived ‘memory’ B and T cells that
recognize the virus patrol the body for
months or years, providing immunity
B-cell
T-cells activate other
immune responses
Content: https://www.nature.com/articles/d41586-020-01221-y
Virus image: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html
In the case of a vaccine, there is no virus
for the immune system to attack.
However, the response triggered by the
vaccine produces the memory so that the
immune system can respond rapidly
upon future exposure

33. Conclusions and caveats
• We don’t know how long immunity will last (months, years?)
• RNA isn’t stable and must be stored at -80 C (-112 F). A typical freezer is -20 C (-4 F). This is
particularly problematic for developing countries without the necessary infrastructure.
• Manufacturing the vaccine will be a monumental task. It will take many many months for it to
be widely available. If we don’t continue with stringent public health measures, the virus will
claim many more lives
• Info is from a press release. We haven’t seen the data yet. Analyses and conclusions need to
be vetted though peer review and approval agencies (e.g., FDA in the US).
This is fantastic news and is very promising. However, there are several items to
keep in mind