In March of 2021, an outbreak of COVID-19 spread through a nursing home in Kentucky. The “Skilled Nursing Facility” had 83 residents (assumed to be in the “older” demographic) and 116 Health Care Personal (HCP) [Which we will assume to generally fall in the “under 65” demographic]. They had all been offered the Pfizer-BioNTech mRNA vaccine.
75 residents (90.4%) and 61 HCP (52.6%) received two doses of the vaccine.
HCP at the nursing home were tested for SARS-CoV-2 twice weekly, so we have a good understanding of when the outbreak started and how it arrived in the facility. After the outbreak was identified, residents were also tested daily with an antigen test. The variant responsible (identified with whole genome sequencing) came from the R1 linage and had several spike protein mutations.
Overall, 26 residents and 20 HCP tested positive for a COVID-19 infection. 18 of those residents and 4 of those HCP had been fully vaccinated.
Lesson 1: Full vaccination does not offer 100% protection from infection, especially in the “older” demographic which may not mount a robust immune response.
Only 28 of these people showed symptoms, 8 of whom were vaccinated, and 20 of whom were un-vaccinated.] 18 people who tested positive did not show symptoms.
Lesson 2: Asymptomatic infections occur.
“Attack rates in unvaccinated residents (75.0%) were 3 times as high as those in vaccinated residents (25.4%)”
Lesson 3: Being vaccinated does provide significant protection from getting infected, even if you are “older”.
“[attack rates] in unvaccinated HCP (29.6%) were 4.1 times as high as those in vaccinated HCP (7.1%)
Lesson 4: Vaccines provide better protection for younger individuals.
Four “possible reinfections” (a positive SARS-CoV-2 test result more than three months after a previous laboratory-confirmed infection) were identified, giving “evidence of limited or waning natural immunity to this [R.1] variant.” All four of these re-infections were symptomatic.
Lesson 5: It is possible to be re-infected by a different variant, even if you have already been infected.
“[Vaccine effectiveness] against hospitalization was 94.4% …among residents; no HCP were hospitalized.”
Lesson 6: Unless you are a nursing home resident, vaccination provides very good protection from hospitalization and death.
“estimated [Vaccine effectiveness] for COVID-19 symptom prevention (86.5% for residents; 87.1% for HCP) demonstrates a strong protective effect of vaccination.”
Lesson 7: Vaccination will protect most people from symptomatic illness.
“The index case occurred in an unvaccinated, symptomatic HCP [Health Care Personal]”
Lesson 8: The more people who are vaccinated, the less likely an outbreak is to occur in the first place.