Our research findings on the impact of vaccines on COVID-19 case and death rates are startlingly clear.
After adjusting for density, poverty levels and government stringency mandates in all 50 states, higher vaccination rates are the most significant factor in reducing COVID-19 cases and deaths.
The study, “The Impact of Vaccination on COVID-19 Case Rates at the State Level,” measured the efficacy of vaccinations in reducing COVID-19 cases and deaths. The research, conducted by Chapman University’s A. Gary Anderson Center for Economic Research, was recently published in the Social Science Research Network.
This study follows up on research published earlier this year in the Business Journal of Bioeconomics, “Examining the Impact of Socioeconomic Variables on COVID-19 Death Rates at the State Level,” and in COVID Economics, “Benefit-cost Analysis of COVID-19 Policy Intervention at the State and National Level.”
Specifically, the research findings show that, on average, the COVID-19 case rate decreased by 86 cases per 100,000 in population for every increase of 1% in the vaccination rate, or for every 10% increase in vaccination rates, case rates decline by 7%. These relationships were found to be significant at high levels of statistical confidence.
By comparing vaccination rates and COVID-19 case rates on a state-by-state basis, it was estimated that as of Aug. 10, vaccinations reduced the case rate (COVID-19 case per 100,000 population in the U.S.) from 9,485 to 4,423—a reduction of 5,062 cases per 100,000.
When states are arranged in quintiles (10 states each) from quintile 1 (10 states with lowest average vaccination rate) to quintile 5 (10 states with highest average vaccination rate), Figure 2 shows the estimated decline in the COVID-19 case rates.
The 10 states with the lowest average vaccination rates (32.4%) experienced an increase of 504 in their average COVID-19 case rate. The three states with the lowest vaccination rates were Idaho, Alabama and Mississippi.
The 10 states with the highest average vaccination rates (49.9%) experienced a decrease of 404 in their average COVID-19 case rate. The three most vaccinated states in our list were Vermont, Connecticut and Rhode Island.
California, with a 59.4% vaccination rate, ranked in the fourth quntile. If Orange County was a state, its 63.3% vaccination rate would put it in the top fifth quintile.
The estimated decline in the projected case rates resulting from vaccinations is equivalent to a total reduction in confirmed COVID-19 cases from 31.3 million (no vaccine) to 14.6 million (with vaccine) for a net reduction of 16.7 million cases. That reduction of 16.7 million cases brought about by vaccinations is estimated to have resulted in 245,000 lives saved in the U.S.
Another important finding in the study that has implications for the future path of COVID-19 is the relationship between COVID-19 cases and deaths. That finding points to a 21-day or three-week lead before changes in confirmed cases lead to confirmed deaths. This three-week lead before the weekly average number of cases most closely affects the weekly average number of deaths can be seen in Figure 3.
Figure 3 shows that the weekly average of total COVID-19 cases peaked during the week of Aug. 27 at 164,000. As might be expected given our research findings, the weekly average of total COVID-19 deaths peaked three weeks later at 2,006 during the week of Sept. 17. Since then, the COVID-19 average weekly caseload has dropped sharply to 74,000. COVID-19 deaths too have fallen sharply to a recent weekly average level of 991. The three-week lead before cases mostly closely result in deaths suggests that the death rate will continue falling.
These empirical findings that clearly point to the efficacy of vaccines in reducing COVID-19 cases and deaths have important implications. Perhaps most important is that the single thing that can be done to help ensure a continuation of the downward path of cases and deaths is to continue increasing the proportion of vaccinated people. This continuation is especially important given the danger of the Delta variant as we move into the peak flu season.
Unfortunately, the average vaccination rate in the U.S. has recently stalled at around 65%. Figure 4 shows the sharp slowdown in changes in average weekly vaccination rates. From the week of Sept. 24 to Oct. 1, the average vaccination rate increased by only 0.4%.
Strategies that might help in voluntarily increasing vaccination rates include multimedia public education campaigns, “Get Out the Vaccine” phone banks, community organizations outreach and broad-based health provider-based efforts.
Given the benefits that higher vaccination rates have on lowering COVID-19 case and death rates, financial incentives from the state and private organizations to people who get vaccinated should also be considered.
Remember, an increase in the vaccination rate from just 65% to 66% is projected, based on the findings of our research, to lead to almost 300,000 fewer cases and 4,000 fewer deaths. That’s a public good that’s worth championing.Â
