Category: COVID-19

April 30, 2021 by Suzanne Judd, LHC Director

Herd immunity occurs when the level of immunity in a population is high enough to prevent the spread of an infectious disease. In other words, when the number of people who are immune to a disease reaches a certain level, the disease no longer has as many chances to spread. This is best achieved through vaccination. In the case of SARS-CoV2, most researchers still agree that at least 70% of the population needs some level of immunity to slow the spread of COVID. One researcher has even started to use “herd immunity” interchangeably with “normality”. On the other hand, several other scientist are questioning if herd immunity is even an achievable goal. Another way to think of herd immunity is to consider it to be the level of immunity others in the community around a person have that will provide a buffer to keep the virus from rapidly spreading.

Calculating Herd Immunity

Calculating the percentage that provides herd immunity is tricky and requires that researchers have first calculated R0, or the rate of the disease’s transmission in a population with no natural immunity to a particular virus. In order to calculate R₀, we need data on the rate of case transmission before anyone in the population was infected or vaccinated. The estimates for R₀ range from 0.8 – 10, which means herd immunity ranges from 50-90%. There are certain populations where diseases spread more rapidly, such as congregate living situations or those who spend long periods in places social settings where food is served.

[Table 1: Range of Possible Herd Immunity Levels for SARS-CoV2 Based on Observed R₀]

Measuring Herd Immunity

Cases are decreasing in Alabama, which is certainly wonderful news! However, this does not mean that we have achieved herd immunity; we still need Alabamians to keep getting vaccinated. Research data suggests that the human body may not have lasting immunity from SARS-CoV2 infection. This means that some people who had immunity from a previous infection (symptomatic or asymptomatic) may not have the same level of immunity today. In order to maintain the level of immunity we currently have in Alabama – which is working to reduce the spread of SARS-CoV2 – we need to continue vaccinating about 100,000 people each week.

Estimating Current Level of Immunity in Alabama

Immunity to SARS-CoV2 could be achieved in three main ways:

1. Immunity without infection – People have antibodies even without a positive test due to asymptomatic infection or lack of test availability early in the pandemic. These people may have had symptoms or may not have had any symptoms. We have no idea how long the immunity lasts in people who did not have symptoms. Early data suggests that immunity in this group may fade as soon as 90 days after antibodies were detected in their blood.
2. Infection – People become sick, test positive, and then recover, having gained antibodies. This is the least desirable way to achieve immunity because some of the people who become sick will never recover. This approach leads to death, hospitalization and long term illness for some of the population.
3. Vaccination – This is the most desirable approach. This leads to the greatest benefit in terms of keeping people from getting sick and potentially dying. The complication rate from the vaccine is not zero but it is extremely low.

[Figure 1: Model Estimating When Alabama Might Experience Herd Immunity]

Model Assumptions

1. At least 70% of the people in the State of Alabama will receive a COVID vaccine in 2021 (number will be easier to achieve if FDA clears the vaccine for 12-15 year-olds)
2. Vaccination is relatively similar across age, race, sex, and geographical location of residence
3. For every 1 positive test, there are 4 individuals who were not tested but have immunity (from undiagnosed, likely asymptomatic, cases)
4. Case rate will continue at current level
5. Vaccine provides some level of protection against variants
6. Immunity begins to fade after 6 months and by 12 months those with previous SARS-CoV2 infection are susceptible to reinfection
7. 30% of those vaccinated already had some level of immunity (this is the primary reason the green curve decreases when vaccinations ramp up)

Which of these assumptions could cause the most problem if they are not met?

1. Vaccination rate: If at least 70% of Alabamans, do not receive the vaccine, community immunity levels will decline. By November of 2021, the total level of immunity in Alabama is estimated to be very similar to where it was in November of 2020 meaning the holiday season might look similar to last year.
2. Vaccination is similar by group: In Alabama, the group that is least likely to pursue the vaccine currently are those aged 16-30. This is also the group with risk behaviors that make them most likely to be in situations where SARS-CoV2 could rapidly spread. SARS-CoV2 does has a lower rate of mortality for young people compared with older individuals but there is now way to know if future variants will behave in the same way. Previous coronavirus pandemics (SARS and MERS) demonstrated a higher mortality rate in young people (1 in 50 aged 25-34 died). Failing to vaccinate 70% of the population could place unvaccinated groups such as children in a very dangerous place if the virus mutates and becomes more lethal.
3. Number of people with immunity but no positive test (asymptomatic individuals): Right now the bulk of the immunity in Alabama is from people who have immunity but have not had a positive COVID test and have not received a vaccine. If there are actually fewer of those individuals in the population, we are only at about 50% of the totally population with some level of immunity which is no where near high enough to stop the spread.

Conclusions and Next Steps

Overall we are in a good place in Alabama at the moment because:

• Cases are decreasing in all districts as vaccination rates continue to rise
• Hospitalizations are decreasing following case decreases

However, if we do not continue to vaccinate at least 100,000 people per week through November 2021, we could be tossed right back into an outbreak. This would force us to make hard decisions about whether or not we can remain open, allow children to go to school in person, and hold major events, which is a place no one wants to return to.

August 4, 2021 by Suzanne Judd, LHC Director

I think I speak for all of us when I say that we had all hoped to be on the path to freedom from COVID-19 by now. Surely, Americans everywhere would like to move on in whatever ways they can – family gatherings, community events, concerts, travel, and so many other things that we’ve been missing for well over a year now seemed within reach just a few weeks ago. Unfortunately, it seems that what progress we had made in overcoming the pandemic is at risk, and we may have to wait a bit longer before we can truly be free from the virus.

Beginning in early June, there were indications in Missouri that we hadn’t quite made it out yet. The delta variant of SARS-CoV-2, the virus that causes COVID-19, began to circulate and cases spiked quite rapidly. As a localized outbreak, the outlook for the rest of the country wasn’t too bleak. However, it wasn’t long until the variant spread down to Florida and the Gulf Coast. Here in Alabama, we are now seeing exactly what it means to have a surge in cases from the delta variant. The figure below uses statistical modeling to predict how many cases we may observe from this new surge.

What do these data mean for hospitalizations?

One piece of data that has become clear is that the vaccine helps to keep people out of the hospital, even if they develop mild symptoms from exposure to a person who has COVID. UAB Hospital has recent recently reported that over 95% of the people hospitalized with COVID-19 had not yet received the COVID-19 vaccine. Since Alabama only has about a 40% vaccination rate right now, this leaves many people at risk of being hospitalized.

What about missing work, school or other activities?

The Southern Alabama curve allows us to estimate the number of people who would be infected, quarantined, or in the hospital at the peak of the surge. If the entire state begins to surge at the rate Southern Alabama is currently surging, there would be about 20% of the population out due to either illness or quarantine for 3 weeks centered around August 26. This assumes that each sick person would come into contact with about 5 other people who would have to quarantine. It also assumes isolation and quarantine to be 14 days. It is really challenging to estimate the number of contacts a person may have or the potential impact of a whole sports team, classroom, or congregation in quarantine. It is possible that 30-50% could be out at one time depending on how people were exposed to an infected individual.

Table 1. Outcomes of Various Transmission Rates
Updated August 12

What can be done?

Absenteeism could be reduced by 37% if masking were required in schools while COVID is circulating at high levels.  Masking would reduce absenteeism to between 6% and 14% in the setting where 5 close contacts have to quarantine. In the case where large groups (classrooms, teams, choirs) have to quarantine, masking could reduce absenteeism from 50% to 37%.

Higher levels of vaccination will have lower levels of absenteeism, since vaccinated people with no symptoms do not have to quarantine and the biggest driver of absenteeism will be quarantine (accounts for 80% of the absenteeism). This has a direct impact on the faculty and students over age 12. It could keep faculty from having to quarantine due to an exposure in their classroom, which will reduce faculty absenteeism.

A school with 90% of the faculty vaccinated would have an absenteeism rate among the faculty of 1% at the peak of this surge compared to 19% in a school with only 10% vaccination rate. The same is true for classrooms where children are 12 and older.

How will we know which of the 3 curves Alabama is on?

The curves above are only predictions. There is uncertainty in the models so it is important to regularly check the data to see how the models are performing. Actual case data can be used to examine how well the model is predicting hospitalizations in Alabama. The figure below shows how well the models are tracking with the number of hospitalizations reported each day. Currently we are much closer to the Southern Alabama path than the India or UK paths but masking, reducing social activities, and increasing vaccinations will all help to bend the curve down so that we do not stay on this path.

May 8, 2020 | Sean McMahon and Sara Harper, LHC Staff

The COVID-19 pandemic seems to have launched us into the great unknown. It’s hard to predict what will change in the world outside the safety of our homes. While news outlets are operating a constant stream of pandemic-related updates, there are other changes going on that don’t make as many headlines. Even in normal times, every policy change leads to unintended consequences, side-effects of the change that are not in line with the goal of the policy. Stay-home orders have certainly slowed the spread of SARS-CoV-2 (the novel coronavirus which causes COVID-19), but what else have those orders done? We’ve rounded up some of the news of the last two months that may be side-effects of staying at home.

Excess Deaths

Excess death data from the CDCUsing data from previous years, the CDC uses statistical modeling to calculate “expected deaths” across the country on a weekly basis. “Excess deaths” is the difference between observed deaths and the expected number. Of course, with over 75,000 COVID-19 deaths in the United States, we would expect roughly that same number in excess deaths. However, in several cities and states the number of excess deaths is larger than their COVID-19 deaths. Death certificates are often submitted without a cause of death with the intention of later completion, so the particular causes can’t be teased out just yet. These deaths stem from a number of possible factors: people may be avoiding healthcare facilities, foregoing medical treatment; people are struggling financially, possibly unable to afford necessities; food insecurity is on the rise. We won’t know exactly what is causing the excess deaths until we have more complete data from death certificates.

Primary Health

On the other end of the healthcare spectrum, a survey of 2,000 primary care physicians reported that approximately 20% predict they will be forced to close within the coming weeks. Privately owned primary care clinics typically operate as small businesses, which have taken a massive blow during the COVID-19 pandemic. Patients aren’t engaging with primary care as we quarantine within our homes, and in consequence, we may see a surge in preventable illnesses in the coming months. Of course, with fewer patients, fewer primary care offices have the resources to remain open. When we emerge from this crisis some families will be left without a primary care physician. Primary care losses can impact treatment access for other deadly diseases like routinely screened cancers, as most treatment referrals come through primary care physicians. Already, lockdowns have resulted in an 86-94% drop in routine cancer screenings and a 60% decrease in chemotherapy attendance.

WHO mental health materialsMental Health

“Are we required to wear masks or not? Are we still seeing 3,000+ deaths a day? All my hometown Facebook friends are posting conspiracy theories. Working from home is not as great as I thought it would be.”

Uncertainty can be hard to deal with. Things are changing so quickly that it’s difficult to keep track of what’s going on. Overall, it seems that mental health and our support systems are taking a hit around the world. Isolation can be a trigger for suicidal ideation, panic attacks, depression, and several other concerns. US alcohol sales spiked at the beginning of the crisis, and “problem drinking” is on the rise in the United Kingdom. Our support systems are also on the rocks. Drug users across Europe cannot access their opioid substitutes and other treatment services. With support groups held online with virtual platforms, participation and accountability may be lower as well. A lack of readily available support services coupled with an economic downturn has led to an increase in deaths from drugs, alcohol and suicide; or what researchers call “deaths of despair”.

Economics

Image of Lucy’s Coffee & Tea. Image from the shop’s Facebook pageOf course, ordering businesses to close has dealt a major blow to the economy. To mitigate this, Congress passed the CARES Act in late March. This $2 trillion stimulus has proven too little, too late in some cases. As of the writing of this blog post, 33.5 million people have filed for unemployment as a result of the pandemic. Over 7 million small businesses are at risk of permanently closing their doors. Several small businesses across the country have already been forced into this. Much to our dismay, Lucy’s Coffee & Tea has shut its doors for good. While some community favorites are forced out of business, other companies find themselves in a position to turn a profit by raising prices on everyday items. Texas Attorney General Ken Paxton, along with a group of individuals in California, has filed a lawsuit against the country’s largest egg producer for price gouging in the midst of a pandemic.

Environment

Not every unintended consequence of stay-home orders has been detrimental. Air quality in the world’s major cities has improved since the lockdowns started. Some cities have seen particulate matter 2.5 (PM 2.5) levels decrease by 60%. This drastic change has increased breathability and visibility in normally crowded cities; quite noticeably in New Delhi. These PM 2.5 declines are beneficial to the environment and human health in general. Lower levels of air pollution also could help fight the novel coronavirus, according to a study from Harvard that found increased susceptibility to COVID-19 in those who have been chronically exposed to high levels of PM 2.5. Air quality will continue to change as countries reopen their economies, hopefully with an increased awareness of sustainability. The National Oceanic and Atmospheric Administration is set to conduct its own studies on the environmental effects of stay-home orders. New Delihi’s India Gate war memorial on 17 October 2019 and on 8 April 2020. Photograph: Anushree Fadnavis/Adnan Abidi/Reuters

More Speculations:

Re-opening strategies put communities of color at greater risk

Some domestic violence aid organizations are worried about a drop in reports, a sentiment echoed by the UN Secretary-General.

Some people may be grappling with a “Quarantine 15,” as physical activity decreases and calorie intake increases.

Experts predict a rise in tuberculosis cases as a result of lockdowns’ impact on treatment and mitigation efforts.