When we read about the effectiveness of Covid 19 vaccines it has to do with clinical trials used to get their approval. What is the real world experience? The short answer is they were even more effective in health care workers than in the clinical trials.
Two Reports Indicate That SARS-CoV-2 Infection Appears Rare In People Who Have Been Vaccinated Against The Virus
The New York Times (3/23, Grady) reports some people who have been vaccinated against SARS-CoV-2 have tested positive for the virus, although the number appears small, based on two reports published in the New England Journal of Medicine. In one study, “four out of 8,121 fully vaccinated employees at the University of Texas Southwestern Medical Center in Dallas became infected.” In another study, “seven out of 14,990 workers at UC San Diego Health and the David Geffen School of Medicine at the University of California, Los Angeles tested positive two or more weeks after receiving a second dose of either the Pfizer-BioNTech or Moderna vaccines.”
Here is the first report, a letter in the New England Journal of Medicine.
TO THE EDITOR:
Here, we report data from the University of Texas Southwestern Medical Center (UTSW), which initiated a program on December 15, 2020, to offer vaccine against SARS-CoV-2 to its frontline employees in phase 1a of vaccination, as directed by the Texas Department of State Health Services. The launch of the vaccination effort coincided with a rapidly escalating number of new SARS-CoV-2 infections in North Texas. This escalation led to the largest surge to date in the region and strained health systems.
In the initial 31 days of the vaccination campaign, 59% of 23,234 UTSW employees received a first dose of either one of the mRNA vaccines and 30% received a second dose. Between December 15, 2020, and January 28, 2021, a total of 350 of the 23,234 employees (1.5%) who were eligible to receive the vaccine were identified as being newly infected with SARS-CoV-2. As shown in Figure 1A, the percentages of persons who became infected differed according to vaccination status, with infections in 234 of 8969 nonvaccinated employees (2.61%; 95% confidence interval [CI], 2.29 to 2.96), 112 of 6144 partially vaccinated employees (1.82%; 95% CI, 1.50 to 2.19), and 4 of 8121 fully vaccinated employees (0.05%; 95% CI, 0.01 to 0.13) (P<0.01 for all pairwise comparisons).
As shown in Figure 1B, from January 9 onward, the actual number of positive tests among all UTSW employees was consistently lower than the number projected on the basis of the actual increasing SARS-CoV-2 positivity rate among patients who presented to our emergency department during this same period and had samples that were tested on polymerase-chain-reaction assay.1 Additional information is provided in the Supplementary Appendix, available with the full text of this letter at NEJM.org.
The effect of vaccination on the preservation of our workforce has been dramatic. We observed a greater than 90% decrease in the number of employees who are either in isolation or quarantine (Fig. S2 in the Supplementary Appendix). Real-world experience with SARS-CoV-2 vaccination at UTSW has shown a marked reduction in the incidence of infections among employees. This decrease has preserved the workforce when it was most needed.
Approximately 70% of our employees were vaccinated in phase 1a by February 4, and 78% were vaccinated in phase 1a by March 5. It is clear that vaccine hesitancy presents an important challenge, even when access is not an obstacle. Addressing the factors underlying this reluctance through insights gained from experience will be essential if the full potential benefit of vaccination in creating a path to normalcy is to be achieved.
William Daniel, M.D.
Marc Nivet, Ed.D.
John Warner, M.D.
Daniel K. Podolsky, M.D.
University of Texas Southwestern Medical Center, Dallas, TX
Here is the second report:
TO THE EDITOR:
Data from phase 3 clinical trials of messenger RNA (mRNA) vaccines through November 2020 showed 94.1% efficacy for the prevention of symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at 14 days after the second dose of the mRNA-1273 vaccine (Moderna)1 and 95% efficacy at 7 days after the second dose of the BNT162b2 vaccine (Pfizer).2 Since the results of these trials were published, a nationwide surge in coronavirus disease 2019 (Covid-19) has been noted, SARS-CoV-2 variants with increased infectivity have emerged, the Food and Drug Administration has granted emergency use authorization for these two mRNA vaccines, and vaccination has been initiated across the United States.
Since the start of the vaccination campaign, the development of Covid-19 has been reported in persons who have received one or both doses of vaccine.3 Both the University of California, San Diego (UCSD) and the University of California, Los Angeles (UCLA) health systems began to vaccinate health care workers on December 16, 2020. On December 2, in addition to defining a low threshold for testing of symptomatic persons, UCSD mandated that asymptomatic health care workers undergo weekly testing by polymerase-chain-reaction (PCR) assay of nasal swabs. On December 26, UCLA instituted an optional testing program for asymptomatic health care workers with PCR assay of nasal swabs. This program has allowed for increased detection of asymptomatic SARS-CoV-2 infections after vaccination.
Pooled data were obtained in deidentified format from an electronic employee health record system at UCSD and UCLA.4 Exemption from institutional review board approval was obtained.
From December 16, 2020, through February 9, 2021, a total of 36,659 health care workers received the first dose of vaccine, and 28,184 of these persons (77%) received the second dose. Among the vaccinated health care workers, 379 unique persons tested positive for SARS-CoV-2 at least 1 day after vaccination, and the majority (71%) of these persons tested positive within the first 2 weeks after the first dose. After receiving both vaccinations, 37 health care workers tested positive; of these workers, 22 had positive test results 1 to 7 days after the second dose. Only 8 health care workers tested positive 8 to 14 days after the second vaccination, and 7 tested positive 15 or more days after the second vaccination (Table 1). As of February 9, a total of 5455 health care workers at UCSD and 9535 at UCLA had received the second dose 2 or more weeks previously; these findings correspond to a positivity rate of 0.05%.
In our cohort, the absolute risk of testing positive for SARS-CoV-2 after vaccination was 1.19% among health care workers at UCSD and 0.97% among those at UCLA; these rates are higher than the risks reported in the trials of mRNA-1273 vaccine1 and BNT162b2 vaccine.2 Possible explanations for this elevated risk include the availability of regular testing for asymptomatic and symptomatic persons at our institutions, a regional surge in infections in Southern California during our vaccination campaigns,5 and differences in demographic characteristics between the trial participants and the health care workers in our cohort. The health care workers were younger and had an overall higher risk of exposure to SARS-CoV-2 than the participants in the clinical trials. In addition, the cutoff dates for reporting in both initial vaccine trials were well before this surge, no testing of asymptomatic persons was included in the BNT162b2 vaccine trial,2 and only a single screening of asymptomatic persons was performed in the mRNA-1273 vaccine trial before the second dose was administered.1
The rarity of positive test results 14 days after administration of the second dose of vaccine is encouraging and suggests that the efficacy of these vaccines is maintained outside the trial setting. These data underscore the critical importance of continued public health mitigation measures (masking, physical distancing, daily symptom screening, and regular testing), even in environments with a high incidence of vaccination, until herd immunity is reached at large.
Jocelyn Keehner, M.D.
Lucy E. Horton, M.D., M.P.H.
UC San Diego Health, San Diego, CA
Michael A. Pfeffer, M.D.
David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, CA
Christopher A. Longhurst, M.D.
Robert T. Schooley, M.D.
UC San Diego Health, San Diego, CA
Judith S. Currier, M.D.
David Geffen School of Medicine at UCLA, Los Angeles, CA
Shira R. Abeles, M.D.
Francesca J. Torriani, M.D.
UC San Diego Health, San Diego, CA