Do people reduce compliance with COVID-19 guidelines following vaccination? A longitudinal analysis of matched UK adults

TL;DR: In the UK COVID-19 Social Study, this article found that compliance with social distancing increased between October 2020 and March 2021, regardless of vaccination status or month of vaccination.

Abstract: IntroductionCOVID-19 vaccines do not confer immediate immunity and vaccinated individuals may still be at risk of transmitting the virus. Governments have not exempted vaccinated individuals from behavioural measures to reduce the spread of COVID-19, such as practicing social distancing. However, vaccinated individuals may have reduced compliance with these measures, given lower perceived risks. MethodsWe used monthly panel data from October 2020 - March 2021 in the UK COVID-19 Social Study to assess changes in compliance following vaccination. Compliance was measured with two items on compliance with guidelines in general and compliance with social distancing. We used matching to create comparable groups of individuals by month of vaccination (January, February, or not vaccinated by February) and fixed effects regression to estimate changes in compliance over the study period. ResultsCompliance increased between October 2020 - March 2021, regardless of vaccination status or month of vaccination. There was no clear evidence that vaccinated individuals decreased compliance relative to those who were not yet vaccinated. ConclusionThere was little evidence that sample members vaccinated in January or February reduced compliance after receiving vaccination for COVID-19. Continued monitoring is required as younger individuals receive the vaccine, lockdown restrictions are lifted and individuals receive second doses of the vaccine.

Summary

Correspondence to

• Liam Wright, Institute of Education, University College London, London WC1H 0AL, UK; liam.
• Given the risk of vaccinated individuals catching and transmitting the virus, understanding whether people comply less following vaccination is important for managing the pandemic.
• The study commenced on 21 March 2020 and involves online weekly (from August 2020, monthly) data collection from participants for the duration of the COVID-19 pandemic in the UK.
• Participants were recruited using three primary approaches.
• There have been a several changes to government rules across this period.

Measures

• Compliance was measured with two questionnaire items, which the authors analysed separately.
• The authors reverse code this item so high scores indicate greater compliance and code those who did not leave them home or meet with others as the highest level of compliance (range 1–5).

Statistical analysis

• First, the authors split their sample into three groups: individuals who first reported being vaccinated in the January wave; individuals who first reported being vaccinated in the February wave and individuals who did not report being vaccinated by February.
• More detail on these variables is given in the online supplemental information.
• The authors assessed match quality as bias <0.1 SD for each covariate, Rubin’s B <0.25, Rubin’s R of 0.5–5, and visual inspection of the distributions for variables used in the Mahalanobis distance matching step.
• In the third step, the authors estimated fixed effects regression models for each matched sample, separately, comparing within- person changes in compliance behaviour by wave of data collection across vaccination groups.
• Due to stipulations set out by the ethics committee, data will be made available at the end of the pandemic.

RESULTS Descriptive statistics

• Descriptive statistics for the full sample are displayed in online supplemental table S1.
• Differences were markedly smaller following matching (online supplemental table S2).
• Figures showing standardised mean differences in the study variables across matched and unmatched samples are displayed in online supplemental figures S2–S4.
• Matching in the January vs February vaccination comparison group was successful, but there were notable differences in the distributions of age and survey date in the January vs nonvaccinated and February vs non- vaccinated groups, respectively.
• As the UK entered a second wave, there were increases in both compliance measures, though with some decrease in social distancing over December.

Vaccinations and compliance behaviour

• The results of the fixed effects regressions are displayed in figure 2.
• There were no statistically significant differences in either compliance measure following vaccination in any matched sample group.
• To explore this, figure 3 displays bar plots for compliance levels at each interview in the January vs February vaccination matched sample.
• In fact, as shown in online supplemental table S2, average compliance levels increased among all groups between October and February in line with the increase in compliance seen in the wider population.

Sensitivity analyses

• Given that fixed effects regressions compare within- person changes in compliance levels across vaccination groups, the authors also repeated the model in (1) using mixed effects modelling, interpreting the term ui as a normally distributed random intercept.
• These regressions tested differences in compliance levels by vaccination status and wave.
• The results are shown in online supplemental figure S10 and are qualitatively similar to those shows in figure 2.

DISCUSSION

• Using panel data from 5 months of the pandemic in the UK, the authors found no clear evidence that receiving a COVID-19 vaccine reduced compliance behaviour.
• Second, their sample was not representative and, moreover, was comprised of individuals who comply more than on average.33.
• The authors results suggest that there is no immediate cause for concern of widespread non- compliance among vaccinated individuals.
• It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer- reviewed.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Do people reduce compliance with covid-19 guidelines following vaccination? a longitudinal analysis of matched uk adults" ?

The authors used monthly panel data from October 2020 to March 2021 in the UK COVID-19 Social Study to assess changes in compliance following vaccination. The authors used matching to create comparable groups of individuals by month of vaccination ( January, February or not vaccinated by February ) and fixed effects regression to estimate changes in compliance over the study period. 

Q2. How many people were vaccinated by the end of 2020?

Seven hundred sixty- eight thousand individuals were vaccinated in England by 27 December 2020, 6.3 million by 28 January 2020 and 14.9 million by 25 February 2020 (1.4%, 11.4%, 27.0% of the population, respectively). 

Q3. Why did citizens express difficulty keeping abreast of latest rules in the UK?

in the UK, citizens have expressed difficultly keeping abreast of latest rules,11–14 due to variations in rules across areas and over time and (speculatively) due to ‘lockdown fatigue’. 

Q4. How many participants were excluded from the study?

The authors used matching in this analysis and excluded participants with missing data on any variable used (n=827; 3.6% of the eligible sample). 

Q5. What was the effect of vaccination on compliance?

Their hypothesis was that, compared with non- vaccinated individuals, compliance would be lower among vaccinated individuals in the months that they were vaccinated, and, given that vaccination does not confer immediate immunity, progressively lower thecopyright. 

Q6. What was the effect of the study on compliance?

by exploiting the longitudinal nature of their sample, the authors were able to use compliance in months prior to vaccination as a placebo test.