Covid-19 Vaccination — What to Expect?

Figure 1. After vaccinated by Pfizer's vaccines, the curve was flattened for ages ≥ 70

If society wants to return to life without social distancing and mask wearing, it needs a vaccine that provides a sufficient amount of what’s known as sterilizing immunity, meaning the drug blocks coronavirus transmission.  In other words, vaccination is the only acceptable path to herd immunity.^[15]

Figure 2. Comparison of New Vaccines

Comparison of Vaccines 

The approved vaccines developed by Pfizer and Moderna use mRNA technology and lipid nanoparticle (LNP) delivery systems, while the approved formulations by AstraZeneca, Johnson and Johnson and Gam-COVID-vac (Sputnik V) contain DNA delivered within non-replicating recombinant adenovirus (AdV) vector systems. 

Both the mRNA and AdV vaccines encode production of the SARS-CoV-2 spike (S) protein, which is the primary target for neutralizing antibodies generated from natural infection and for therapeutic monoclonal antibodies.

Both vaccine types generate significant neutralizing antibody titres and virus-specific T cell responses as measured in blood 2–4 weeks post inoculation.^[29]

Pfizer was the first manufacturer to request emergency use authorization. To know if you are safe to get the Pfizer/BioNTech Covid-19 vaccine, please read the below article:

A guide to who can safely get the Pfizer/BioNTech Covid-19 vaccine

Figure 3. J&J Vaccine vs mRNA Vaccines

Figure 4.  COVID-19 vaccines: modes of immune activation (source: [29])

Potential Side Effects after Vaccination

Mild-to-moderate Side Effects

Pfizer and its German partner BioNTech SE said on Nov. 18 that no serious safety concerns were observed in their late-stage trial. Among participants who got the two-dose vaccine regimen, side effects included 

• Fatigue (3.8%)
• Headache (2%) 

Older adults reported fewer and milder adverse events. In an earlier trial, the companies identified cases of mild-to-moderate fever.

Moderna, meanwhile, said on Nov. 16 that it had also identified no serious safety concerns in its late-stage trial. Mild-to-moderate side effects included 

• Fatigue (9.7%)
• Muscle or joint pain (5.2%) 
• Headache (4.5%) 
• Injection-site pain (2.7%)

The side effects were more common after the second dose of the two-dose vaccine.

“These are things you expect from a vaccine. It actually means that it's working,” Dr. Ramers said. “That’s your immune system learning from that vaccine how to fight that bad virus.”

Serious Side Effects—Bell’s Palsy^[1]

The FDA also looked for signs of any serious side effects in the Pfizer's trial of 44,000 volunteers. The agency noted there were four cases of temporary facial paralysis called Bell’s palsy in the vaccine group and none in the placebo group.

Despite the apparent imbalance, the FDA scientists noted the numbers were so small the cases could have been caused by something other than the vaccine. In a large group of people, a certain number of cases of Bell’s palsy are expected to occur because the disorder can be caused by several pathogens.

The number of cases in the vaccine group did not exceed what regulators call the background rate, meaning the number of cases that would be expected to occur in the general public.

Bell’s palsy is temporary and treatable. Actress Angelina Jolie announced in 2017 she experienced a bout of Bell’s palsy and fully recovered.

No Way the Vaccine Can Cause COVID-19

Because of the mechanics of how Pfizer’s mRNA vaccine trains the body to build an immune response, there is no way the vaccine can cause COVID-19, Dr. Ramers noted. The vaccine does not contain actual virus or viral particles.

Protection from COVID19 after Vaccination

Cumulative Incidence Curves 

Based on the cumulative incidence curve for the all-available efficacy population after Dose 1, (Figure 4), COVID-19 disease onset appears to occur similarly for both BNT162b2 and placebo groups until approximately 14 days after Dose 1, at which time point, the curves diverge, with more cases accumulating in the placebo group than in the BNT162b2 group, and there does not appear to be evidence of waning protection during the follow-up time of approximately 2 months following the second dose that is being evaluated at this point in time. 

Prof. Akiko Iwasaki had also commented on Figure 5:

People who received the Pfizer vaccine are protected from COVID19 as early as 12-13 days post first dose (likely reflecting the increase in antibody response).

Figure 5.  Cumulative Incidence Curves for the First COVID-19 Occurrence After Dose 1^[2]

Why do we need a booster shots?

Both the mRNA and AdV vaccines require two doses spaced 3–4 weeks apart to promote optimal protection (Figure 6, 7) and have been associated with mild to moderate side effects, including injection site pain, transient fever and chills, which can be augmented with the second dose. 

This secondary enhancement of the inflammatory response can derive from short-term changes to innate cells like macrophages through a phenomenon called ‘trained immunity’,^[30] and/or from activation of memory T cells and B cells generated from the initial injection. 

Type I interferon has been shown to amplify T cell memory and promote B cell differentiation and survival, suggesting vaccine-associated inflammation in the booster can further promote generation and perpetuation of long-term immunological memory.

Figure 6.  The importance of 2nd shot which is especially for older people

Should people who’ve already had Covid-19 be vaccinated too?

The short answer is yes, which is based on immunologists' recommendations.  Read [14] for more details.

Figure 7.  Somatic hypermutation leading to affinity maturation

Latest Developments

Read this companion article here.

References

1. What the FDA's review reveals about Pfizer's COVID-19 vaccine
2. FDA Briefing Document Pfizer-BioNTech COVID-19 Vaccine
3. COVID-10 Vaccine F&Q
4. FDA Says 2 Participants In Pfizer COVID Vaccine Trial Have Died
• To be sure, it's unclear whether the participants who died succumbed to vaccine-related complications, or whether they even received a vaccine at all (they could have received a placebo).
5. U.K. Says Those With Severe Allergy Should Avoid Pfizer Shot
6. Don't mix Sputnik vaccine with alcohol, says Russian official. Some recoil
7. Explainer: What the UK cases of allergic reaction mean for Pfizer's COVID-19 vaccine
8. Pfizer Shot Gets FDA Advisers’ Nod as Agency Decision Nears
9. Vaccine bootcamp (nice animation)
10. Peru suspends Sinopharm COVID-19 vaccine trial after 'adverse event'
11. SARS-CoV-2 Reinfection Is Rare but Possible
12. The Coronavirus Vaccine Could Be the Ultimate Gateway Drug
13. Health worker in Alaska had serious allergic reaction after Pfizer's vaccine - NYT
14. Yes, people who’ve had Covid-19 can still benefit from the vaccine
15. Vaccination is the only acceptable path to herd immunity
16. South Africa identifies new coronavirus strain causing surge in cases
17. FDA grants authorization to Moderna’s Covid-19 vaccine, the second in the U.S.
18. FDA investigating five allergic reactions after Pfizer shot in U.S
19. Australia halts home-made COVID vaccine production on HIV false positives
20. UKvariant with 9 mutations in the Spike Protein
21. New Coronavirus Strain: Will Vaccines Still Work On Variant Found In The U.K.?
22. Scientists Scramble To Identify Culprit Behind Covid Vaccine Allergic Reactions
23. Vaccine overdose puts German care workers in hospital
24. Travel Insurers Likely To Make Vaccination A Requirement, New Report Finds
25. Spain Plans A "Registry" For Those Who Refuse COVID Vaccine
26. Britain grants approval to coronavirus vaccine by Oxford and AstraZeneca
27. Interim Clinical Considerations for Use of mRNA COVID-19 Vaccines Currently Authorized in the United States (CDC)
28. Myths of Vaccine Manufacturing
29. COVID-19 vaccines: modes of immune activation and future challenges
30. Yao, Y. et al. Induction of autonomous memory alveolar macrophages requires t cell help and is critical to trained immunity. Cell 175, 1634–1650 (2018).
31. Pfizer/BioNtech And Moderna MRNA Covid-19 Vaccines Closely Mimic The Immune Response Of Natural SARS-CoV-2 Infections
32. COVID vaccines and blood clots: what researchers know so far