UK vaccines data

Here’s what we know so far about the after effects of the Pfizer COVID vaccine

Here’s what we know so far about the after effects of the Oxford AstraZeneca COVID vaccine

How to tell the difference between COVID-19 symptoms and vaccine after effects

Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study

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Pfizer-BioNTech (BNT162b2)

Oxford-AstraZeneca (ChAdOx1 nCoV-19)

Safety and effectiveness in UK community setting

1,607,620 users (2·4% of the UK population)

Methods

Prospective observational study

Self-reported systemic and local side-effects within 8 days

After one or two doses

Infection rates, after vaccine, diagnosed by PCR or lateral flow

Unvaccinated controls

Findings

Dec 8th 2020, and March 10th 2021

Vaccinated reporters, n = 627 383

Reactogenicity, (common, expected)

Systemic side-effects

Fatigue and headache (about 4% each)

Most frequently within the first 24 h

Lasted a mean of 1·01 days

Fever

Chills or shivers

Nausea

Diarrhoea

Muscle pains

Joint pains

Local side effects

Tenderness and local pain

Redness

Swollen armpit glands

Warmth

Itch

Bruising

Pfizer

One dose, 282, 103 (13% SSE) (71.9% LSE)

Two doses, 28, 207 (22% SSE) (68.5% LSE)

Median, 41 days apart

Oxford AZ

One dose, 345 280 (33.7% SSE) (58.7% LSE)

In those with past infection after Pfizer

SSE x 2.9

LSE x 1.2

In those with past infection after Oxford AZ

SSE x 1.6

LSE x 1.4

Vaccinated people who became infected

Vaccine group, 3,106 of 103,622

Unvaccinated controls, 50,340 of 464,356

Reductions in infection risk

Started at 12 days after the first dose, to 21 days

Reaching - 60% Oxford AZ

Reaching - 58% for the Pfizer

Longer term benefits of vaccination after Pfizer

RR, 21 to 44 days - 69%

RR, 45 to 59 days, - 72%

In conclusion, short-term adverse effects of both vaccines are moderate in frequency, mild in severity, and short-lived.

Adverse effects are more frequently reported in younger individuals, women, and among those who previously had COVID-19.

The post-vaccine symptoms (both systemic and local) often last 1–2 days from the injection.

Our data could be used to inform people on the likelihood of side-effects on the basis of their age and sex and the type of vaccine being administered.

Furthermore, our data support results from randomised controlled trials in a large community-based scenario showing evidence of reduction in infection after 12 days and substantial protection after 3 weeks.