Vaccine Effectivness

Comparing Vaccines

So.. just how good are the different vaccines? Note that you can’t reeeeally do a straight comparison of one vax to another because the trials measured different things with different populations and different variant mixes at different times. As a good article in The Economist says, “the gap in reported efficacy may say more about the trials than about the vaccines themselves.”

Not only that, but some trials had such low numbers of severe cases even in the placebo branch that it was really hard to draw good conclusions.

With that disclaimer, I present data below. Also, this review article from 25 September 2021 has a very exhaustive list.

BrandAgainstWhereFirst shot+MSecond Shot+N
PfizerinfectionIsrael / HCW52·4%90.5%
PfizerinfectionUK / HCW72%86%
PfizersymptomaticIsrael /HCW85%
PfizerhospitalizationIsrael74% 87%
Pfizersevere diseaseIsrael62%92%
AZsymptomaticSouth Africa B.1.351x10.6%
SinopharmhospitalizationBahrain, UAE, Egypt, Jordanx78.7%
CoronaVacinfectionBrazil / Sao Paolox51.8-70%
PfizerinfectionSouth Korea89.7%x
AZinfectionSouth Korea86.0%x
Pfizerhospitalization over 80 y/oUK81%93%
AZhospitalization over 80 y/oUK73%x
Pfizer or AZhospitalization over 70 y/oUK84%81%
Johnson & JohnsoninfectionUSA76.7%N/A
Johnson & Johnsonmoderate illnessUSA72%N/A
Johnson & JohnsoninfectionSouth Africa52%N/A
Johnson & Johnsonmild to moderate illnessSouth Africa64%N/A
Johnson & Johnsonsevere illnessSouth Africa82%N/A
Johnson & Johnsonmoderate illnessBrazil66.2%N/A
Johnson & Johnsonmild to moderate illnessBrazil68%N/A
Johnson & Johnsonsevere illnessBrazil88%N/A
AZinfectionUK (B117)65%?
PfizerinfectionUK (B117)65%70%
PfizerinfectionEngland (B117)70%85%
SinovacdeathsIndonesia HCWx98%
SinovacinfectionIndonesia HCW13%94%
Pfizer or ModernainfectionOntario48-71%91%
Pfizer or ModernasevereOntario62-91%98%
Sputnik Vsymptomatic infection ages 60-79Argentinax78.6%
Sputnik Vhospitalization ages 60-79Argentinax87.6%
Sputnik Vdeaths ages 60-79Argentinax84.7%
mRNAany infectionUS HCW (CDC)81%91%
CureVacinfection (prelim)49%
Soberanainfection? dose 2 out of 3 PRELIMCuba?62%
Abdalainfection? 3 out of 3 PRELIMCuba?92.3%
NovavaxinfectionMexico, US90%
Pfizerhospitalization of over 80 y/osUK79·3%N/A
AZhospitalization of over 80 y/osUK80·4%N/A
Pfizerall asymptomaticIsrael HCW65.1%
Pfizerinfectious asymptomaticIsrael HCW69.6%
Pfizerall symptomaticIsrael HCW89.7%
Pfizerinfectious symptomaticIsrael HCW88.1%
AZasymptomatic infection in high-risk groupsEngland60%81%
Pfizersymptomatic infection in high-risk groupsEngland60%
Pfizersymptomatic infection in high-risk groups over 65England89%
AZsymptomatic infection in high-risk groups over 65England80%
AZ/Pfizersymptomatic infection in immunosuppressedEngland4%74%
Pfizersymptomatic in age 16-64UK48.6%93.3%
AZsymptomatic in age 16-64UK50.2%78.0%
Pfizersymptomatic in age 65+UK56.6%86.7%
AZsymptomatic in age 65+UK60.9%76.4%
Pfizersymptomatic in immunosuppressedUK15.9%73.0%
AZsymptomatic in immunosuppressedUK43.9%74.6%%
mRNAhospitalization, allUS86.9%
mRNAhospitalization, 18-49 y/oUS97.3%
mRNAhospitalization in immunosuppressedUS59.2%
Pfizerasymptomatic infection in pregnantIsrael67%, 71%97%
Pfizersymptomatic in pregnantIsrael66%, 76%97%
Pfizerhospitalization in pregnantIsrael89%
Pfizersymptomatic in all veteransUS84.0%96.25
Modernasymptomatic in all veteransUS85.7%98.2%
Pfizer 6 month studysymptomatic 7 days to 2 months post dose2US / South Africa / Brazil / Argentina / Germany / Turkey91.1%96.2%
Pfizer 6 month studysymptomatic at 4-6 months post dose2US / South Africa / Brazil / Argentina / Germany / Turkey83.7%
6 month study
severeUS / South Africa / Brazil / Argentina / Germany / Turkey96.7%
AZasymptomatic to household contactsNetherlands58%
Pfizerasymptomatic to household contactsNetherlands70%
Modernaasymptomatic to household contactsNetherlands88%
J&Jasymptomatic to household contactsNetherlands77%
Modernaasymptomatic infectionSouthern California72.7%
Modernasymptomatic infectionSoCal88.3%
Johnson & Johnsoninfection, corrected for under-reportingUSA79%
Johnson & Johnson infection, not corrected for under-reportingUSA69%
Johnson & Johnsonhospitalization, corrected for under-reportingUSA81%
Johnson & Johnsonhospitalization, not corrected for under-reportingUSA73%
Johnson & Johnsonsymptomatic infectionUSA94%
Johnson & Johnsonsymptomatic infectionworld outside USA75%
Johnson & Johnsonhospitalizationmany countries100%
Pfizersymptomatic infectionUSA, health care workers77.6%88.8%
Modernasymptomatic infectionUSA, health care workers88.9%96.3%
CloverinfectionPhilippines, Colombia, South Africa, Brazil, Belgium79%
CloverhospitalizationPhilippines, Colombia, South Africa, Brazil, Belgium100%
Moderna5-month followup, asymptomatic infectionUSA, high-risk individuals63.0%
Moderna5-month followup, symptomatic infectionUSA, high-risk individuals93.2%
Moderna5-month followup, severe diseaseUSA, high-risk individuals98.2%
mRNAhospitalization, 65-79 y/osPortugal78%94%
mRNAhospitalization, over 80 y/oPortugal55%82%
mRNAdeath, 65-79 y/osPortugal77%96%
mRNAdeath, over 80 y/osPortugal56%81%
AZICU or death[1]Malaysia96%
Pfizerinfection after 1 monthCalifornia88%
Pfizerinfection after 5 monthsCalifornia47%
Pfizerinfection after 16 weeksNorth Carolina81%91%
Novavaxsymptomatic infectionUSA / Mexico90.4%
Novavaxhospitalization / ICU / deathUSA / Mexico100%
AZdeath, 40-60 y/oScotland88%
Pfizerdeath, 40-60 y/oScotland95%
AZdeath, over 60 y/oScotland90%
Pfizerdeath, over 60 y/oScotland87%
AZdeath, all agesScotland90%
Pfizerdeath, all agesScotland91%
Pfizerinfection, 12-17 y/oIsrael66%90%
Pfizersymptomatic infection, 12-17 y/oIsrael82%93%
Modernainfection, male prisonersCalifornia56.6%
Modernasymptomatic infection, male prisonersCalifornia84.2%
mRNAinfectionBritish Columbia90%
mRNAinfection Quebec88%
AZinfectionBritish Columbia71%
AZ+mRNAinfectionBritish Columbia90%
mRNAhospitalizationBritish Columbia98%
AZhospitalizationBritish Columbia94%
AZ+mRNAhospitalizationBritish Columbia99%
mRNAinfection given 3-4 week dose intervalBritish Columbia85%
mRNAinfection given 3-4 week dose intervalQuebec79%
mRNAinfection given 7-8 week dose intervalBritish Columbia91%
mRNAinfection given 7-8 week dose intervalQuebec89%
mRNAinfection given 3-4 week dose intervalBritish Columbia and Quebec93%
mRNAinfection given 7-8 week dose intervalBritish Columbia and Quebec99%
Covaxinsymptomatic infectionIndia77.8%
Covaxinsevere diseaseIndia93·4%
Covaxinsymptomatic infection, hospital staff, from DeltaIndia50%
Soberana 02symptomatic infectionCuba71%
Soberana 02severe diseaseCuba63%
Soberana 02deathCuba59%
Soberana 02 with Soberana Plussymptomatic infectionCuba92.4%
Soberana 02 with Soberana Plussevere diseaseCuba100%
Soberana 02 with Soberana PlusdeathCuba100%
mRNAinfection of military veteransUSA69%
mRNAdeath of military veteransUSA86%
Pfizerhospitalization for 12-18 y/osUSA (23 states)94%
PfizerICU for 12-18 y/osUSA (23 states)98%
Pfizerdeath for 12-18 y/osUSA (23 states)100%

[1] In Malaysia, AZ is mostly given to younger people, which potentially makes it look better than it is.

See also

This article compares Moderna and Pfizer, though TBH I think they are close enough to not worry about.

Non-Coronavirus Vaccines against COVID

There have been a bunch of studies on how well non-coronavirus vaccines are against COVID. Surprisingly, many give some protection. See my page on that.

Efficacy against Variants of Concern

See above caveats about doing comparisons between vaccines (after fully dosed unless otherwise specified).

BrandWhereAgainstvs. Classicvs. Alpha / B.1.1.7vs. Beta / B.1.351vs Gamma / P.1vs. Delta / B.1.617.2
Pfizer95%excellentprob okay?unknown
PfizerQatarinfection 1 dosex29.5%16.9%x
PfizerQatarhospitalization 1 dosex54.1%0.0%[3]
AZUK / Brazil / South Africasymptomatic?82%74.9%22%unknown
NovavaxUK / South Africasymptomatic?95.6% or 89.3%85.6%60%unknown
J&J (Janssen)US / Latin America / South Africasymptomatic?72% [1]unknown57%unknown
SinovacBrazil / Turkey / Indonesia / Chilesymptomatic?83.7%? [2]
AZUKsymptomatic 1 dose51%33%
AZUKsymptomatic 2 doses66%60%
PfizerUKsymptomatic 1 dose49%33%
PfizerUKsymptomatic 2 doses93%88%
PfizerUKhospitalization 1 dose83%94%
PfizerUKhospitalization 2 doses95%96%
AZUKhospitalization 1 dose76%71%
AZUKhospitalization 2 doses86%92%
NovavaxSouth Africainfection, HIV+49%
NovavaxSouth Africainfection, HIV-55%
ModernaOntarioinfection 1 dose54%83%77%see Beta [4]72%
PfizerOntarioinfection 1 dose61%66%60%see Beta
AZOntarioinfection 1 dose67%64%48%see Beta
ModernaOntarioinfection 2 doses89%92%xsee Beta
PfizerOntarioinfection 2 doses93%89%84%see Beta
ModernaOntariohospitalization or death 1 dose57%79%xsee Beta
PfizerOntariohospitalization or death 1 dose 68%80%77%see Beta
AZOntariohospitalization or death 1 dosex85%83%see Beta
ModernaOntariohospitalization or death 2 doses96%94%xxx
PfizerOntariohospitalization or death 2 doses96%95%95%see Beta
ModernaQatarinfection 1 dose88.1%61.3%
ModernaQatarinfection 2 doses100%96.4%
AZBrazilsymptomatic infection63.6%
AZEnglandinfection 1 dose48.7%30.7%
AZEnglandinfection 2 doses74.5%67.0%
PfizerEnglandinfection 1 dose47.5%35.6%
PfizerEnglandinfection 2 doses93.7%88.0%
J&JSouth Africahospitalization 67%71%
PfizerDenmarkasymptomatic infection81.0%78.8%
AZ or AZ+mRNADenmarkasymptomatic infection95.9%88.1%
ModernaDenmarkasymptomatic infection93.2%73.7%
AZ or AZ+mRNADenmarkhospitalizationN/A96.6%
PfizerSouthern Californiainfection75%
Johnson & JohnsonUSAinfection78%[5]
Johnson & JohnsonUSAhospitalization85%[5]
CloverPhilippines, Colombia, South Africa, Brazil, Belgiuminfection91.8%78.7%
CloverPhilippines, Colombia, South Africa, Brazil, Belgiumhospitalization100%100%

“or” means that different sources reported different things

[1] US study.  66% in Latin America (Brazil, Colombia, Peru, Chile, Argentina, Mexico)

[2] Trial was in Brazil, but unknown how much P.1 was in the sample.

[3] From the counts of who was hospitalized and who wasn’t, this didn’t look to me like it should be 0%, but I couldn’t completely understand the data.

[4] For the Ontario multi-VOC study, they grouped Beta and Gamma together.

[5] For the Johnson & Johnson study, this data was from June/July 2021 in US states where Delta was predominant.

Efficacy against Omicron

(The chart above was getting too wide and crowded.)

BrandLocationAgainstWhen# dosesVE
Pfizer or AZEnglandhospitalizationomicron wave2 or 381%
Pfizer or AZEnglandhospitalizationomicron wave388%
J&JSouth Africahospitalization after 0-13 days2021-Nov-15 to 2021-Dec-20263%
J&JSouth Africahospitalization after 14-27 days2021-Nov-15 to 2021-Dec-20284%
J&JSouth Africahospitalization after 1-2 months2021-Nov-15 to 2021-Dec-20285%
ModernaCaliforniainfection at 14-90 days2021-12-06 to 2021-12-23230.4%
ModernaCaliforniainfection2021-12-06 to 2021-12-23362.5%
PfizerCaliforniaEmergency Department admission, <3 months post vaxDec 01, 2021 through Jan 11, 2022260%
PfizerCaliforniaEmergency Department admission, over 3 months post vaxDec 01, 2021 through Jan 11, 2022241%
PfizerCaliforniaEmergency Department admission, <3 months post vaxDec 01, 2021 through Jan 11, 2022378%
PfizerCaliforniaEmergency Department admission, over 3 months post vaxDec 01, 2021 through Jan 11, 2022348%
PfizerCaliforniahospital admissionDec 01, 2021 through Jan 11, 2022268%
PfizerCaliforniahospital admissionDec 01, 2021 through Jan 11, 2022289%

Dose Interval

What is the optimal interval?

It is my understanding that in most vaccines, you want a fairly long interval between dose 1 and dose 2. The immune system needs some time to learn and train from the first dose.

Why then, are were the recommended intervals so short initially? Because the vaccine makers were in a real hurry. They did the absolute shortest interval that they thought they could get away with.

There have been a lot of people who have had longer intervals since then. It was a bit of a calculated gamble to do so before the data was in, but it was apparently a pretty safe bet, since all other vaccines did better with a longer dose interval.

Since then, there have been a few studies.

  • This study of Pfizer in people over 80 found that they generated 2.5x as many antibodies with a 12-week interval than with a 4-week interval.
  • This study of AZ found that antibodies were higher with a 12-week dose interval than an interval shorter than six weeks.
  • This study of AZ found that antibodies were higher the longer the dosing interval was. They studied up to 44 weeks.
  • This study of Pfizer found that neutralizing antibodies were higher for a long dosing interval (6-14 weeks) compared to a short interval (3-4 weeks).
  • This study of Pfizer found that a 16-week interval was better than a 4 week interval.
  • This study of Pfizer and Moderna found that antibody levels were higher in people who had a 6 to 7 week interval than in people who had a 3 to 4 week interval.

There also have been literally millions of people who have had a longer interval. For example, in BC, most of the 2.3M people who have gotten a second dose (as of 18 July 2021) have had a dose interval longer than 7 weeks. (Mine was ten weeks; my partner’s eleven.) The UK has also had a long dose interval.

Waning Effectiveness

There have been a bunch of studies documenting a significant decrease in effectiveness against infection over time. There is a small drop against hospitalization and death, but not nearly as large.

It is not entirely surprising that the vaccines are less effective against infection but still very good against severe disease. Antibodies are the first line of defence, and they are kind of designed to go away when they are not needed, but to get called back in force when there is an infection. It takes a few days for a new antibody army to get raised, however, which gives time for infection to take hold.

The first Pfizer clinical trials said that the vaccine efficacy after only one dose was 92%, but this re-examination of the clinical data gives much better numbers:

I believe I saw another paper which said that the efficacy declined quite a bit after five weeks, but I would have to dig a bit harder to find that the paper.

This preprint did a meta-analysis of a bunch of waning studies. They found that vaccine effectiveness dropped a lot between 1 and 6 months after the second dose:

asymptomatic infectionall-18.5%
asymptomatic infectionolder-19.9%
symptomatic infectionall-25.4%
symptomatic infectionolder-32.0%
severe diseaseall-8.0%
severe diseaseolder-9.7%

This study from BC and Quebec showed a lot less waning — more like 10% than 20-30% — for long dose intervals than for short dose intervals:

This image has an empty alt attribute; its file name is Screen-Shot-2021-11-22-at-2.16.56-PM-1024x625.png

This preprint reports waning of two doses of AZ in Scotland and Brazil. The vaccine effectiveness against severe disease was:

2-3 weeks14-15 weeks18-19 weeks

Note that there are lot of papers on waning effectiveness, I just got bored writing them all down.


This publication from Public Health England says that the vaccine effectiveness was 93.1% for those over 50 with AZ+AZ+Pfizer and 94.0% for Pfizer+Pfizer+Pfizer.

This big study which looked at Pfizer, Moderna, AZ, J&J, Novavax, CureVac, and Valneva as boosters for AZ/AZ or Pfizer/Pfizer found that (broadly speaking), the more mRNA, the better. (See my 2 Dec 2021 analysis for more detail and nuance.)

<there have been a bunch more booster studies, they all show that a booster increases effectiveness against infection, at least in the short term… I need to add them in…>

This preprint says that the J&J boosters (i.e. second dose) in South Africa does well. Its effectiveness against infection was:

  • 63% effective 0-13 days after the second dose
  • 84% effective 14-27 days days after the second dose
  • 85% effective 1-2 months days after the second dose