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Ask Dr. Halverson: Don’t be surprised when vaccinated people get infected

web 4 17 Halverson photoBy Dr. Jim Halverson

Coronavirus vaccination efforts locally and in the United States are proceeding at ever-increasing rates. Currently, the United States is vaccinating an average of 2.5 million people per day. In Ventura County, we are averaging more than 30,000 vaccinations per week, including more than 2,200 per week at Nordhoff High School. Ojai has the second-highest percentage of people vaccinated in Ventura County.

Even with all of this good news, it is inevitable that we will begin to be made aware of fully vaccinated people coming down with COVID-19. Though unfortunate for the individual, there is absolutely no cause for concern that this may indicate that vaccinations are not the answer to ending the pandemic.  A review of the vaccine trials that took place last summer and fall gives us the reason that infections in fully vaccinated people are to be expected.

All three of the currently FDA-approved vaccines went through very rigorous trials for which protocols, testing procedures, results and follow-up were all made public for all of us to review if we wish. The Food and Drug Administration criteria were made clear from the start. The vaccine candidate had to show at least 50% effectiveness in reducing the number of COVID-19 cases. Amazingly, both the Pfizer and Moderna vaccines showed a 95% reduction in symptomatic cases and the Johnson and Johnson vaccine a 72% reduction. In absolute numbers, the 30,000 vaccinated individuals in both the Pfizer and Moderna trials developed 10 infections over the several months of monitoring after being fully vaccinated. The 30,000 individuals in each unvaccinated group developed 190. No vaccinated individuals who did develop infections required hospitalization or died.

These breakthrough infections, which occur when fully vaccinated people are infected by the pathogen that their shots were designed to protect against, are an entirely expected part of any vaccination process.  They are the simple proof that no vaccination is a perfect preventative.

Nearly 150 million vaccine doses have been administered as of March 30. Breakthrough infections have been mostly mild, reaffirming the idea that inoculations are powerful weapons against serious disease, hospitalization and death. The goal of vaccination is not eradication, as I explained last week. Vaccination should help us reach a relatively peaceful coexistence with the virus, with the risk of infection and severity of disease at a tolerable low.

It is not always clear why breakthrough infections occur. There are three main factors in play. The first factor is the virus itself. It is well documented that the current vaccines are not as effective against variants that originated in Brazil and South Africa. Fortunately, there have been a very small number of these cases in the United States. Two California variants, B.1.427 and B.1.429, have shown slightly decreased immune response to antibodies produced by the vaccines. It is not clear if that will result in a decrease in vaccine effectiveness as other immune defenses, such as T-cells, are also produced by the vaccines. The longer the virus stays at higher levels in our population (the current average of 60,000 new cases per day in the United States is still very high), the greater the likelihood that more-resistant variants will occur.

The second factor is the amount of exposure to the virus itself, called the viral load. If vaccinated people are spending time with groups of unvaccinated people in places where the virus is circulating in high levels, that will raise their chance of getting COVID-19. Being exposed to high viral loads can overwhelm the sturdiest of immune defenses, if given the chance.

The third factor is each of us. Immunity in every vaccinated individual will vary by some degree. Some people might have underlying conditions (such as morbid obesity, advanced age, significant kidney or liver disease) that decrease their immune response to the vaccine. Others might simply, by chance, make fewer or less potent antibodies and T-cells that can nip a coronavirus infection in the bud. The range of vaccine responses is not a variation of two- to threefold. It is much greater. Being vaccinated does not mean you are immune. It means you are better protected against severe infection.

Fortunately, a team at the Centers for Disease Control is tracking breakthrough cases and will soon start reporting case counts and outcomes of those as well as any patterns related to where, or in whom, these infections are occurring. This data can help the experts figure out why post vaccination infections happen, and how they might be stopped.

Most of the time, vaccines are far more likely to offer some help than none. Serious disease, hospitalization, and even death will still occur. In the unlikely case post-vaccination infections climb to unexpectantly high rates, backup plans will quickly kick into gear. Some recipients might get an additional shot to bolster their immune response; others might be administered a new vaccine that has been updated to account for a new viral variant.

The more people we vaccinate, the more breakthrough cases there will be, in absolute numbers. But the rate at which they appear will decline as rising levels of population immunity cut the conduits that the virus needs to travel. People with lackluster responses to vaccines, as well as those who can’t or won’t get vaccinated, will get protection from the many millions of us in whom the shot did work. 

In the meantime, continue to observe all social-distancing measures and wear a mask as recommended. Getting the absolute number of cases down in our area will lessen the chance that we will be infected by the virus and dramatically decrease the chance that new variants will be found in our county.

Stay hopeful, stay diligent, stay properly informed, stay safe and stay well.

— Dr. Jim Halverson is a longtime Ojai physician who writes a weekly column on COVID-19 for the Ojai Valley News.

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