Overall vaccine uptake was 60.8% in our hospital. Whilst this is encouraging it is unclear what proportion need to be vaccinated to confer herd immunity. Several estimates have put the proportion between 70–80% across a population . It is likely that the current rate will provide some protection against nosocomial spread, but hospital populations are dynamic with patients, often with relatives or carers, attending frequently. Therefore, it remains uncertain whether there will be an impact on the recommended level of infection prevention & control precautions.
We saw differences in uptake between groups. There was little difference between the sexes, but staff were more likely to be vaccinated with increasing age. This may be important if there are areas where staff are typically younger, for example general wards.
We saw lower uptake in nursing and clinical support staff, but the lowest rates were seen in portering, domestic and catering staff, all of whom are potentially more at risk of coming into close contact with patients with COVID or their environment.
It was striking that uptake is lower amongst Black / Afro-Caribbean staff and those of mixed heritage. This is concerning as these groups have been disproportionately adversely affected by COVID and potentially remain at risk. Additionally, these groups are over-represented amongst the staff groups above. Furthermore, London has a higher proportion of staff from these groups when compared with the rest of the UK which may have an impact on a health service level .
It is clear that, to improve uptake, more work is needed to understand the reasons why it is lower in certain groups. It would be important to know whether this represents an issue with access or whether there is true hesitancy in receiving the vaccine and if so, what are the reasons why staff may not wish to be vaccinated. Some work has already begun around this nationally . We are currently conducting a survey locally to explore reasons. We are also conducting small focus groups and other engagement sessions over the coming weeks.
We did not see any serious adverse events and we did not routinely collect data on minor side effects. Consequently, we do not have enough data from our cohort to make reliable conclusions around safety, however, early indications are that the Pfizer-BioNTech vaccine appears to be safe.
Our 7-day rolling average of cases mirrored the London 7 day rolling average. This is not surprising as our hospital falls within the London area and suggests that a substantial proportion of cases amongst our staff reflect what is happening in the local community rather than nosocomial spread within our institution. Our rate appeared to rise, peak, and start to fall slightly before the London rate, and we do not have an explanation for this. We saw relatively fewer cases after Christmas and during the first 2 weeks of January and we postulate that this was for 2 main reasons. Firstly, the onsite testing centre closed for a period over Christmas & New Year. Secondly, we suspect there was an effect due to more staff than usual being on annual leave.
Once the vaccination campaign began a clear difference in the groups testing positive for COVID began to emerge. Cases initially occurred in the unvaccinated and recently vaccinated groups, however, the groups diverged by 14 days with almost all subsequent cases occurring in the unvaccinated group. This appears to be similar to what was reported in the initial efficacy study and most likely reflects the development of an effective immune response in the vaccinated group . It is reassuring that the survival analysis beyond 14 days, showed an 80% lower risk of COVID infection in vaccinated HCWs. Although this is a statistically significant difference in risk, there is a large amount of uncertainty around our estimate, with the ‘true’ risk reduction being anywhere from 21–95%. Larger studies are required to verify our findings.
Importantly, our small study shows that the protective effect of this vaccine continues beyond 21 days in an hospital setting following the first dose. This is reassuring given that the National Strategy is to delay administration of the 2nd dose of the vaccine to 90 days .