Herd Immunity – Do We Wait?

April 13, 2021
As more populations are vaccinated worldwide, it is becoming increasingly apparent to many of us that a COVID-19 vaccine jab (or two) is not necessarily a golden ticket back to a normal life.

In the U.S., for example, the CDC has urged individuals who are fully vaccinated to continue wearing masks, practice social distancing and try to avoid crowds. Fully vaccinated travelers are also still expected to produce negative infection tests prior to departure and on arrival, and many countries still require a two-week mandatory quarantine period. This is because, while many COVID-19 vaccines have a good chance of suppressing illness and preventing symptomatic disease, the big unknown is how well they prevent the virus from spreading.

There seems to be a consensus that we need to wait until enough people have been vaccinated and herd immunity is achieved before we can safely resume our pre-COVID activities.

Herd immunity occurs when enough in a community are immune that they act as a shield against viral transmission, preventing the vulnerable from getting infected.

But here’s the problem we have in waiting. According to experts such as Dr. Anthony Fauci, up to 90% of the population would need to be immune to COVID-19 to achieve herd immunity. Calculating this percentage depends on how transmissible the virus is. For example, measles is highly transmissible, with each infected person able to infect 12 to 18 more, and as such it requires about 95% of people to be immune for herd immunity to occur.

Even if vaccine uptake is high, reaching this goal of herd immunity is looking increasingly unrealistic, scientists report. A University of Sydney study estimates that the vaccines being administered in Australia (Pfizer and AstraZeneca) will not provide the country with herd immunity. More recently, a publication in Nature was released explaining ‘Five reasons why COVID herd immunity is probably impossible’. In summary, these are:

1. It’s unclear whether vaccines prevent transmission
2. Vaccine roll-out is uneven
3. New variants change the herd-immunity equation
4. Immunity might not last forever
5. Vaccines might make us complacent with social distancing behaviours

These are all logical and compelling reasons. At the core of them all is that long-lasting immunity is not guaranteed after COVID-19 vaccination. We still don’t know how effective vaccines will be at providing this level of immunity, whether it will stand up against new variants, and how long it will last. Duration of post-vaccine immunity will likely follow similar patterns to natural immunity, which shows antibody levels waning for nearly 40% of people within the first 6 months of recovery.

Chia et al, 2021: The Lancet. Key figure shows negative or waning antibody levels in a collective of 67% of post-COVID participants.

So, frustrating as it is, vaccines could get us most of the way to herd immunity but are very unlikely to get us all the way there. We can’t achieve herd immunity through natural infection either – Brazil and India’s second waves are evidence of this.

Solving the seemingly impossible - What are we waiting for?

While achieving herd immunity might seem impossible, we can move forward by measuring immunity in individuals. From a small finger-prick sample, a Quantitative Immunity Test can do this. It first measures the level of antibodies directed against the virus. This can then be compared against a threshold to determine if a person has sufficient immunity.

Because this tool has the power to verify a person’s immune status, it will enable populations to return to a normal life. and there’s no need to wait for herd immunity, or even for widespread vaccination.

Suspect you’re immune from past infection, but haven’t yet been vaccinated?
Recently vaccinated, but unsure if your immune system has built a barrier to infection?

A quantitative immunity test can answer these questions.

Orbis has developed a quantitative immunity test that can rapidly measure COVID-19 antibodies in a non-lab environment, ideal for deployment at clinics and airports around the world. Learn more here.