Does a higher vaccination rate lead to fewer cases? We analyzed Horry County’s data
More than a year after Horry County reported its first coronavirus case, the COVID-19 vaccine became widely available for residents, a welcome step in the progression out of the pandemic expected to drastically reduce infections and deaths.
Doctors and public health professionals touted the vaccine as the great white hope of the pandemic, and people clamored for appointments to get the shot.
Months later, Horry County is back in a worrisome situation as case counts and hospitalizations overwhelmed hospitals at the end of August. Despite the vaccine’s availability, cases rose. They surged at levels reminiscent of a pre-vaccine world, thanks largely to the highly contagious delta variant and the vaccine uptake coming to a near halt as the county reached about half of its population vaccinated.
Across Horry County, around 58% of eligible people have been vaccinated, but the vaccination rate and coronavirus spread vary widely in Horry County depending on region. A Sun News analysis found a connection between the percentage of residents in a given ZIP code who were vaccinated and how easily the connection was spread.
The stats in Horry County
Using data from the S.C. Department of Health and Environmental Control (DHEC) on vaccination rates and case counts starting when the vaccine became available to most South Carolina adults on March first through Sept. 21, The Sun News calculated which ZIP codes have seen the highest spread in the last several months in comparison to respective vaccination rates.
It’s not a direct correlation, and other factors such as mask use, social distancing and the ability of residents to travel freely to other areas with different vaccination rates have an impact on an area’s incidence rate.
“If we weren’t such a transient society nowadays, the data would probably correlate nicely, but we are,” said Dr. Paul Richardson, chief medical officer at Conway Medical Center. “People … go from Horry to Georgetown County all the time.”
The demographic of a certain ZIP code, along with the potential for activities that could spread COVID-19 could also be responsible for a higher incidence rate, even if a high vaccination rate has been recorded.
“I look on TV and there’s 80,000 people at a football game,” said Dr. William Epperson, medical director of primary care at Tidelands Health. “If those people are vaccinated, I’m not really very concerned about them so much, but younger people have a much less vaccination rate. That’s why I believe the spread is there, they have closer contact and a lower vaccine rate.”
How local ZIP codes stack up
In general, the ZIP codes with the highest vaccination rates were among those with the lowest incidence rate, the analysis found.
For example, the ZIP code with the highest vaccination rate — ZIP code 29572 at around 80% vaccinated — had an incidence rate of around 45 cases per 1,000 residents in the last several months. That’s the third-lowest incidence rate in Horry County’s 16 ZIP codes.
The two ZIP codes with the next-highest vaccination rates — 29582 at around 79% and 29566 at around 74% — also fall within the lower incidence rates seen in Horry County.
The 29582 ZIP code, which covers North Myrtle Beach, reported an incidence rate of around 48 cases per 1,000 residents since March 31. In the Little River area, the 29566 ZIP code recorded around 58 cases per 1,000 residents in that time period.
Conversely, the highest incidence rate was logged in the Galivants Ferry area, where around 111 cases per 1,000 residents occurred since late March. The area has around 38% of its residents vaccinated.
The analysis found the 29581 ZIP code had the lowest vaccination rate at just above a quarter of residents vaccinated. In this area, which covers Nichols and Ketchuptown in western Horry County, the incidence rate was around 48 cases per 1,000 residents.
Why are Horry County’s rates so varied?
Since the vaccine’s initial rollout, public health officials have been clear that breakthrough cases are possible, meaning just because someone is vaccinated doesn’t mean they won’t get sick. But being vaccinated is proven to lower your risk of severe COVID-19, meaning you’d be less likely to be hospitalized or die due to the virus if you’ve been fully vaccinated.
Over the last few weeks, more than 90% of admitted COVID-19 patients have been unvaccinated Richardson said. Even when vaccinated coronavirus patients are admitted to the hospital, they’re less likely to need intensive care or ventilators, and less likely to die of complications.
DHEC doesn’t track hospitalizations by ZIP code, so it’s not clear just how much vaccination rates have affected hospitalizations in different areas of Horry County. In the last two months, hospitals have faced mounting need for resources due to rising COVID-19 infections, and Tidelands Health operated at more than 100% capacity for more than a week last month.
The different vaccination rates by ZIP code could be explained by a number of factors, as people have varying reasons for resisting the vaccine.
But at this point in the pandemic, avoiding getting the shot has less to do with accessibility and more to do with personal opinions, Epperson pointed out.
“Different ZIP codes have amazingly different vaccination cases, well why would that be the case?” he said. “Because individuals in different ZIP codes probably have some similarities in where they came from, their social determinants of health, that sort of thing that we address.”
The vaccination rate of different areas is important, especially to reach the elusive “herd immunity” level necessary to largely escape the virus’ grasp. The percentage of the population immunized against the virus to reach herd immunity is unclear as the virus is new and evolving. Estimates indicate the immunization rate to reach an acceptable level of herd immunity is at least 70-80%.
While the vaccination rates differ widely by ZIP code, it’s also important to consider the demographics of each ZIP code. The COVID-19 vaccine has only been authorized for people ages 12 and up as of now, and it’s possible some areas with older populations have a higher vaccination rate because there aren’t as many kids who are ineligible for the shot currently.
But the delta variant appears to be driving infections among a younger and unvaccinated population. In the month of August, nearly 900 kids and teens had COVID-19, far more than any other month in 2021.
Though a high vaccination rate isn’t the only thing that could lower an infection rate in any given area, doctors and public health professionals maintain getting inoculated is the best way to protect yourself and others from severe illness and even death.
“My stance on vaccinations has not changed one bit,” Richardson said. “I do think it is the best weapon we have, there’s no doubt in my mind.”
This story was originally published September 27, 2021 at 2:17 PM with the headline "Does a higher vaccination rate lead to fewer cases? We analyzed Horry County’s data."
