Vaccines alone will not bring herd immunity

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Person wearing mask with bandage on arm. Image credit: CDC/Unsplash

There is nothing new under the sun. Substitute the word "pandemic" or "COVID-19" for "sun" and the sentiment remains the same. Canada is now into the 15th month of this strange, new world, even though our country was late in declaring the pandemic's arrival.

Media reports focus on several themes:

  • statistics relaying information about cases, hospitalizations, ICU admissions, and deaths
  • efficacy of various vaccines, their timing and potential side-effects
  • virus variants
  • vaccination supplies, deliveries, distribution, eligibility and rates of uptake
  • vaccine hesitancy
  • public health measures, including mask-wearing, hand-washing and physical distancing
  • pandemic-related restrictions, including closure/part closure of various businesses and assorted outdoor activities, both public and private.

It's a lot to digest, especially with myriad announcements from public health, governments of all levels, vaccine organizations and manufacturers, physicians, and other medical workers, scientists, epidemiologists, and international bodies such as the World Health Organization (WHO), as well as COVAX and the Global Vaccine Alliance (Gavi).

One day, the United States is touted for the large percentage of adults who have received at least one dose of a vaccine; there are media reports that unused vaccines are being discarded every day. The same day, Canada is criticized for lagging behind in putting needles in arms and several Canadian premiers are asking governors across their borders to vaccinate essential Canadian workers who cross the border to work in the U.S.

Throw the U.K. and Israel into the mix, and add in experience from New Zealand, and things only get more confusing. The next day, reports shift: the U.S. is falling behind; easing and removal of government-imposed restrictions are blamed. Canada improves its vaccine position, only moderately. It is impossible to declare "who's on first."

And then there is herd immunity. It is heralded as the signal for pandemic-free or restriction-reduced life. Unfortunately, experts, be they from government, public health or the medical or scientific field, have varying perspectives on the definition of herd immunity and the estimated timeline to achieve it.

Wikipedia has a definition worth reviewing:

"Herd immunity is a form of indirect protection from infectious disease that can occur… when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity." 

What does this really mean? The key to herd immunity is the R value. Originally used in demographic studies, R stood for reproduction, used to measure how fast the population grew or waned. When used to determine how fast an infectious disease is spreading, R stands for replication. The higher the infection rate, the more people can contract the disease through exposure to an already-infected person who has yet to develop antibodies. With low infection rates, the disease essentially runs out of people to infect. As with seasonal flus, this is the goal. And it is a moving target.

There are many factors considered in the R value:

  • how infections are spread indoors and out, through direct contact and/or air-borne transmission
  • how long the incubation period lasts for new infections (the asymptomatic period)
  • how long it takes for infected people to create antibodies to the disease
  • how long the antibodies last and how effective they will be.

Clearly, we still do not know with certainty the answers to these questions. We still need to test and trace and then test and trace again. And we still need to conduct research and to accept that things will change. And then they will change again.

Initially, taming the pandemic or "flattening the curve," was meant to prevent overwhelming the hospital system. What is sometimes forgotten is that even with the pandemic, people still have accidents, still are diagnosed with cancer and heart disease and still have chronic conditions requiring hospital care.

If hospitals are overwhelmed with COVID cases, these diagnostic, preventive and restorative non-COVID services are cut back or entirely shut down. Already, research shows that Canadians have avoided attending both hospitals and other medical care because of fear of becoming infected with COVID-19. The effects of ignoring and postponing medical and surgical treatments can be dire and long-lasting.

Still, until vaccines were created, keeping hospital beds available for COVID-19 care was essential. And it is worth recalling that initial projections suggested widespread availability of vaccines in two years at the earliest. We are ahead of that projection.

When the pandemic first arrived, public health measures were imposed to limit exposure between members of the public.

Once vaccines were approved and distribution began, combatting the COVID-19 pandemic had another, very powerful tool. Similarly, as successful treatment protocols were discovered, fewer cases advanced to the most critical stage; ICU cases and deaths in hospital declined.

Unfortunately, the success in reducing R values from vaccines increased the emphasis on herd immunity. The lower R value was interpreted as reducing the need for restrictions and these were eased. In some jurisdictions, they were eliminated. These actions counteracted the downward trends and, along with new variants, led to second, third -- and now, forecast fourth waves.

The R values and the nearness of the goal of herd immunity, however defined, ebbed and flowed. They will continue to do so, despite more people being vaccinated. Ironically, epidemiologists suggest that people who are vaccine-hesitant may become more so as other people's vaccinations reduce the spread of the infection. The vaccine-hesitant may feel justified in believing that their own vaccinations are not needed.

Even now, politicians are anticipating pandemic restriction-reduced summers. These announcements reflect the number of vaccinated Canadians. But, with Canadians suffering from COVID fatigue and economic considerations, politicians are once again turning the focus away from public health measures.

We seem incapable of carrying two thoughts at the same time. Shots in arms are essential. But vaccines alone will not bring herd immunity. Lockdowns and stay-at-home orders are essential. But restrictions alone will not bring herd immunity. It takes both. Isn't it time we realized this?

Evelyn H. Lazare is a retired health-care planner, strategist and executive. Currently living in Ottawa, she now devotes her writing primarily to novels.

Image credit: CDC/Unsplash

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