Question: Can we fully vaccinated people do in-person events with other fully vaccinated people when we will still have vulnerable children at home?
Answer: Accumulating evidence indicates that vaccinated people can safely be together with other vaccinated people with very low risk of infection/transmission. Add a few safety precautions– like gathering outside with fewer than 10 fully vaccinated people– and the very low risk is even further mitigated, likely approaching zero (though I don’t have a point estimate to provide).
What’s the concern? The vaccine trials were testing how well the vaccines prevent disease and severe disease, not how well the vaccines prevent infection and transmission. This important nuance has limited our initial understanding of whether vaccinated people can become infected and transmit the virus to others. If vaccinated people are mingling together, they are increasing their risk of potential exposure, could then unknowingly carry the virus back to their homes, and infect their children or others in their household who have not yet been vaccinated.
What does accumulating evidence say? Real-world data from Israel and the UK (see Q&A of 2/24 and Q&A of 2/18), and most recently the US (described herein) indicate that vaccination greatly reduces risk of infection and likely reduces risk of onward transmission. Just yesterday, CDC’s MMWR published a study examining infection rates among healthcare workers after vaccination, “Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers — Eight U.S. Locations, December 2020–March 2021.” Based on data collected from study participants (3,950 healthcare workers) over the course of 13 consecutive weeks, researchers found that “Three PCR-confirmed infections occurred during 78,902 person-days with full immunization (≥14 days after second dose; incidence rate = 0.04/1,000 person-days). Estimated adjusted vaccine effectiveness of full immunization was 90% (95% confidence interval [CI] = 68%–97%); vaccine effectiveness of partial immunization was 80% (95% CI = 59%–90%)” (Figure 1)
Figure 1. mRNA vaccines are highly effective in preventing infections (from CDC)
