L14: COVID Virus: Vaccines and Drug Development Flashcards
what are the three parts of a simplified schematic of a virus?
these are in most viruses, but specifically the SARS-CoV-2 virus
- viral nucleic acid on the inside = recipe for viral infection
- proteins and lipids on the outer coat
- spike proteins on the outside
what is the human gene/protein that accepts the SARS-CoV-2 virus
ACE2 protein
- binds tightly to the spike proteins on the covid virus
what happens when the virus is inside the cell? (3 steps)
- it releases its own genetic material, so its viral RNA
- the infected human cell reads the genetic material and begins to make parts of the virus (could be the s-spike protein – we are the bioactive part)
- the new copies of the virus are assembled and carried to the outside of the cell to infect nearby healthy cells
what are coronaviruses? what does corona mean? how common is it?
- a large family of viruses that can infect humans or animals
-“Corona” = the spike proteins look like the corona (crown) of the sun
- Cause illnesses that range from the common cold to the 2003 SARS and 2012 MERS outbreaks
what is the transmissibility of covid-19? how do we measure it?
- it is a highly transmissible virus like other known viral infections
- R0 tells us how contagious a disease is
- Average # of individuals that get infected from one infectious person
- Ideally, we want R0 ≤1
R0s for common viruses:
COVID = 2-2.5
SARS= 2-4
Ebola = 1.6-2
what is the fatality of COVID
- it has a low fatality rate compared to other diseases like SARS, tuberculosis, Ebola, MERS etc.
what are the several approches that have been used to develop covid-19 vaccines?
(4)
Traditional approaches:
1. Killed or attenuated virus
- viruses that are very weak or have been killed entirely
- used to stimulate our immune system to recognize surface proteins on the virus and mount and immune response
- doesnt cause disease, but allows the immune system to recognize the foreign virus
- Protein
- use pieces of proteins from the pathogen to do the same as above
- used commonly in the SARS-CoV-2 spike protein
Novel approaches:
1. viral vectors
- using viruses to actually carry material for us into the host cells so our body can recognize it and fight against it
- using adenovirus to carry the SARS-CoV-2 DNA into the host cells
- ex. oxford/astra zeneca, and johnson&johnson
- DNA / RNA
- DNA -> RNA -> Protein
- protein has been traditionally used to mount an immune response
- can create the protein in different ways: through mRNA or DNA
- ex. Moderna, Pfizer
what are the three approaches to trigger an immune response
- using a whole virus or bacterium
- parts that trigger the immune system (ex. spike proteins)
- just the genetic material in the nucleic acid
all make effective vaccines
what are viral vectors – type of vaccine
- Modified viruses that deliver the target antigens genetic code so the body can recognize and fight against it
- When the modified virus is administered as a vaccine, it enters cells and instructs them to produce the antigen proteins, triggering an immune response
- Vectors do not contain disease-causing genes
- Can be broken down into 2 types:
–> Replicating
–> Non-replicating
what are DNA/RNA types of vaccines
- DNA or RNA (nucleic acids) that codes for a single antigen protein so that the body can recognize this bad protein and fight against it
- RNA especially are charged and dont sit stabley in the environment… thus:
- Can be encapsulated in a vessicle/ fatty coat (or bubble) to fuse with the cell membrane and deliver the genetic material for the protein code inside the person to create the vaccine
what are protein based vaccines
- A protein is extracted from the virus, purified, and injected as a vaccine
- these are different kinds of biologics
- acts as a bioreactor
- Mimic the coronavirus to trigger an immune response
how are killed or weakened viruses made?
- Killed virus – virus is inactivated using chemicals or heat
- Weakened virus – virus has mutations in its genome (genetically engineered), so it doesn’t express its viral proteins as well
Why did we not find a treatment for SARS given that another viral disease is likely to reoccur?
OG virus was in 2003 called SARS-CoV
COVID was in 2019 and was SARS-CoV-2
- After the SARS outbreak in 2003, vaccines against SARS-CoV were developed
- However, development was halted as virus was eradicated and diminished
–> the Rnot and lethality of the virus was low and thus eventually stopped - No commercial reason to revive development at the time, took time and money
how is the clinical trial process during the pandemic different to what it is like typically?
It was accelerated tremendously!
- typically takes 15 years to develop vaccine but for covid they developed it in 10 months to 1.5 years
- they had pre-exisiting data from SARS-CoV and MERS-CoV and toxicology reports which limited the testing from 4+ years to months
- they overlapped the phase 1, 2, 3 trials instead of waiting till completion for one to start the other
- they really riskly started mass producing the vaccines even before getting approval so they could distribute it asap if approved.
what was diversity like in early clinical trials for a covid vaccine
very high diversity rates because we didnt know which type of vaccine would work (mRNA, viral vector etc..)
Describe the comirnaty vaccine of COVID made by BioNTech & Pfizer. what is it, how was it tested in each phase
what was it:
- mRNA that encodes the spike protein enclosed in a lipid nanoparticle (person converts mRNA to protein and mounts immune response)
- Two doses administered intramuscularly 3 weeks apart
- Health Canada authorized this vaccine with conditions on December 9, 2020
Phase 1:
- Placebo-controlled, observer-blind, dose-escalation trial (n=195)
- Evaluated the safety of different vaccine doses of 2 vaccine candidates – has some differences in the formulation. tested in elderly also (BNT162b1 and BNT162b2)
Phase 2/3:
- 360 adults
- Evaluated the efficacy of 30 μg BNT162B2 vaccine dose against placebo
- Data pooled with Phase 3 trial
Phase 3:
- ~44,000 adolescents and adults
- Evaluated the efficacy of 30 μg
against placebo (let both groups roam and tested if they would be effected)
- Vaccine was 95% effective in preventing COVID-19
how is the efficacy rate calculated for pfizer vaccine?
- Had a 20,000 large group for both placebo and vaccine
- after they roamed, 162 placebo participants were infected, and 8 vaccine participants were infected.
- the infection risk was calculated bt dividing infected by initial group size
- relative risk was calculated by subtracting infection risk percents
- efficacy rate = relative infection risk/ placebo infection risk
= 95%
Describe the Spikevax vaccine of COVID made by Moderna. what is it, how was it tested in each phase
what is it:
- mRNA that encodes the spike protein enclosed in a lipid nanoparticle
- Two doses administered intramuscularly 4 weeks apart
- Health Canada authorized this vaccine with conditions on December 23, 2020
Phase 1:
- 120 healthy adults
- Evaluated the safety of 25-250
μg vaccine doses
- Vaccine was generally safe and well tolerated – what we are testing in phase 1
Phase 2:
- 600 healthy adults
- Evaluated the efficacy of 50 and 100 μg vaccine doses against placebo
Phase 3:
- ~30,000 adults
- Evaluated the efficacy of 100 μg vaccine against placebo
- Vaccine was 94.1% effective in preventing COVID-19
how long did it take for the Pfizer vaccine to be made
11 months to a year.
- SARS-CoV-2 genome was released late feb
- preclinical started right after
- Phase 1, 2 started late april
- phase 2, 3 started late july
- rolling submission of data started in october
- EUA use started december
why did we get COVID vaccines so quickly? ten reasons
- pandemic plans were already in place
- China identified the novel coronavirus early on
- Tremendous funding was provided immediately
- Speedy clinical trials process
- Quick commencement of vaccine trials
- Availability of research data
- Studies garnered many volunteers
- Rapid results from trials
- Early vaccines worked well
- Regulation took place while the studies were continuing
what won the nobel prize in 2023
mRNA vaccines for COVID-19:
Katalin Karikó and Drew Weissman
for physiology or medicine
why were infographics so important in covid posters — NYC’s approach
helped everyone understand what was in and what was not in the vaccines so people know correct information about the vaccine
these infographics were shown in NYC and steered people to be vaccinated
explain canada’s novel approach to a covid vaccine and why it was discontinued
Medicago’s plant based COVID-19 vaccine
Medicago’s plant based COVID-19 vaccine
- Virus-like particles are made in plants, which are then harvested and purified
- 71% efficacy against COVID-19
- Approved in Feb 2022 by Health Canada
- However, financial and production difficulties, did not bring vaccine to market
what was Nuvaxovid (Novovax), another canada-approved vaccine for covid, and what did it contain
Nuvaxovid (Novovax)
- protein-based vaccine
–> This kind of vaccine has been used for >30 years (e.g. hepatitis B vaccine) - given as primary (first vaccine) or Omicron XBB.1.5 subvariant vaccine
- Contains:
–> Spike protein, produced by insect cells (bio-reactor)
–> Immune system stimulant, derived from the soapbark tree (so that it will react against the protein)
–> Health Canada approval December 2023
