August 20, 2021, 4:25 p.m. Michael Devitt — On Aug. 18, the CDC published three new studies that reviewed the effectiveness of the Pfizer-BioNTech, Moderna and Janssen/Johnson & Johnson vaccines in preventing infections and hospitalizations attributable to SARS-CoV-2, the virus that causes COVID-19.
The results of these studies, posted as Morbidity and Mortality Weekly Report early release studies on the MMWR website, illustrate the effect of the delta variant of SARS-CoV-2 on these health outcomes as the pandemic continues in its second year.
At the same time, the results indicate that COVID-19 vaccination remains highly effective in reducing the incidence of infection and hospitalization across a wide range of patient populations, and that the vaccines also provide a substantial layer of protection against the delta variant of the virus.
“These studies once again demonstrate that the COVID-19 vaccines remain remarkably effective, particularly at preventing severe illness and hospitalization,” Sarah Coles, M.D., chair of the AAFP Commission on Health of the Public and Science and an assistant professor at the University of Arizona College of Medicine-Phoenix Family Medicine Residency, told AAFP News. “Vaccination is a critical component of our fight to end the pandemic.”
The first report focused on a specific population — namely, adults residing in New York state. Like many states, New York underwent a phased COVID-19 vaccination process, with all individuals 16 and older eligible for vaccination beginning April 6, 2021.
The report’s authors collected information from four databases to build a surveillance-based cohort of patients 18 and older. To allow time for significant numbers of the population to reach full immunity, the authors analyzed COVID-19 data beginning the week of May 3 through the week beginning July 19.
Breakthrough infections were defined as new cases among people who were fully vaccinated on the day of specimen collection. Hospitalizations among those with breakthrough infection were defined as new hospital admissions among people who were fully vaccinated on the reporting day. Individuals who were partially vaccinated were excluded from any analyses.
The analysis found that between May 3 and July 25, overall age-adjusted vaccine effectiveness against new COVID-19 cases declined from almost 92% to just under 80%. At the same time, however, vaccine effectiveness against COVID-19 hospitalization stayed between 91.9% and 95.3%. The authors noted that vaccine effectiveness against hospitalization remained stable even as prevalence of the delta variant in the northeastern United States increased from less than 2% to more than 80% during the study period.
The analysis also found that new case rates and new hospitalization rates were substantially higher among unvaccinated individuals compared with fully vaccinated individuals from week to week, and remained higher for the duration of the study period. Based on average population sizes, the analysis showed that for the entirety of the study period, on average, unvaccinated people experienced new cases of COVID-19 at a rate more than eight times higher than those who were fully vaccinated, and experienced hospitalizations at a rate nearly 12 times higher than fully vaccinated people.
“This study’s findings suggest currently available vaccines have high effectiveness for preventing laboratory-confirmed SARS-CoV-2 infection and COVID-19 hospitalization,” the authors wrote, adding, “These findings support a multipronged approach to reducing new COVID-19 hospitalizations and cases, centered on vaccination and including other approaches such as masking and physical distancing.”
The second report examined the effectiveness of the Pfizer-BioNTech and Moderna vaccines in preventing hospitalizations due to COVID-19 infections over a period of several months. To test the durability of the vaccines, researchers conducted a case-control analysis of more than 3,000 adult patients in 18 states who were admitted to a hospital between March 11, 2021, and July 14, 2021.
The case group consisted of patients who presented with symptoms of COVID-19 infection and had received a positive SARS-CoV-2 test result. One control group consisted of patients with COVID-19-like illness who tested negative for SARS-CoV-2; a second control group also tested negative for SARS-CoV-2 but did not present to the hospital with COVID-19-like symptoms.
Patients in all three groups were asked a variety of questions, including history of COVID-19 vaccination, chronic conditions, and the presence of immunocompromising conditions such as HIV infection or rheumatoid arthritis. Fully vaccinated individuals were defined as having received both doses of an authorized mRNA COVID-19 vaccine, with the second dose received at least 14 days before the onset of illness. A total of 1,129 patients (141 cases, 988 controls) were considered fully vaccinated.
Vaccine effectiveness in preventing hospitalizations was measured by comparing the odds of being fully vaccinated versus unvaccinated between case patients and control patients. Additional models were used to determine effectiveness based on the time from receipt of the second vaccine dose and illness onset.
The analysis showed that among fully vaccinated individuals, overall vaccine effectiveness against COVID-19 hospitalization was 86% over the course of the study period. While effectiveness was lower in adults with immunocompromising conditions (63%) compared with those considered immunocompetent (90%), it was sustained over the study time period.
Among patients with illness onset, vaccine effectiveness was 87% between the months of March and May and dropped only slightly to 84% during June and July, a period that coincided with increased prevalence of the delta variant throughout most of the United States. However, this drop was not significant. More data will be needed to understand the full impact of the delta variant on vaccine effectiveness.
“These data provide evidence for sustained high protection from severe COVID-19 requiring hospitalization for up to 24 weeks among fully vaccinated adults, which is consistent with data demonstrating mRNA COVID-19 vaccines have the capacity to induce durable immunity, particularly in limiting the severity of disease,” the authors stated.
“To reduce their risk for hospitalization, all eligible persons should be offered COVID-19 vaccination,” they added. “Continued monitoring of vaccine effectiveness against infection and severe disease is needed as the elapsed time since vaccination increases and new SARS-CoV-2 variants emerge.”
The third report examined the effectiveness of the Pfizer-BioNTech and Moderna vaccines in preventing SARS-CoV-2 infection among residents of nursing homes or skilled nursing facilities.
Researchers used weekly reports from more than 14,000 facilities throughout the United States to measure the effectiveness of the vaccines during three consecutive time intervals:
Analysis of the reports found that among fully vaccinated individuals (those who received two doses at least 14 days earlier) vaccine effectiveness for any mRNA vaccine in preventing SARS-CoV-2 infection was 74.7% during the pre-delta period. Effectiveness declined to 67.5% in the intermediate period, and to 53.1% once the delta variant became predominant.
“To prevent transmission of SARS-CoV-2 in nursing homes, these findings highlight the critical importance of COVID-19 vaccination of staff members, residents and visitors, and adherence to rigorous COVID-19 prevention strategies,” the report’s authors stated.
Research has shown that primary care physicians provide the majority of vaccinations in the United States. Taking that evidence into consideration, Coles emphasized the role that family physicians can play to increase community vaccination rates.
“Family physicians must continue to be those front-line champions and encourage their patients and communities to get vaccinated,” Coles said. “We know that a recommendation from a patient’s trusted primary care physician is one of the most effective strategies to get people vaccinated.”
Coles also advised FPs to consider various issues that may have caused patients to not be vaccinated against COVID-19, and to continue to work to help patients overcome barriers to vaccination.
“We cannot give up on people who have not yet received the vaccine. Most people are not truly opposed to vaccination, but they may face barriers to access the vaccine, might have questions about the safety and efficacy of the vaccine, or may be swimming in misinformation making it very difficult to choose vaccination. Family physicians are best situated to address these issues,” said Coles.
“We must continue to fight to increase vaccine access and reduce barriers by addressing the social determinants of health,” she added. “We need to meet people where they are, listen with respect and empathy to their concerns, answer questions honestly without judgment, and help guide patients to trusted sources of information.”
As has been done throughout the pandemic, AAFP expert staff remain committed to updating content and resources on AAFP.org and familydoctor.org as new information is available. Visit the Academy’s COVID-19 Vaccine webpage to find the latest on COVID-19 vaccine data, educational resources and advocacy.
Additionally, the AAFP is maintaining and updating its main COVID-19 webpage with new information related to post-COVID syndrome, monoclonal antibody therapy and other resources for patient care on an ongoing basis.