‘Breakthrough cases’ of COVID-19 in four Oregonians after fully vaccinated: Should we be alarmed? Expert says “No”

Dr. Louis Picker, associate director and professor at the Vaccine and Gene Therapy Institute at Oregon Health and Science University, said there is no reason to be alarmed about “breakthrough cases” of COVID-19 after vaccination. 



A “breakthrough case” is an infection from an illness in which the vaccinated person becomes sick from the same illness the vaccine is trying to prevent.

This comes after the Oregon Health Authority (OHA) announced Friday that four Oregonians who had completed both doses for the vaccine tested positive for the virus. Two of these cases are in Lane County and the other two are in Yamhill County. 

The four people tested positive at least 14 days after receiving their final dose of the vaccine, and their illnesses range from asymptomatic to mild symptoms.

The OHA is investigating but said that this is not unexpected:

“Clinical trials of both vaccines presently in use included breakthrough cases. In those cases, even though the participants got COVID-19, the vaccines reduced the severity of illness.”

No vaccine is 100% effective, said Picker.

“These [breakthrough cases] are expected for all vaccines. Very few, I don’t think any, come to 100%. Even the measles vaccine is [around] 98%, that means that people who are vaccinated, for a variety of reasons, might still, if they’re exposed, get infected.”

Picker said that it is very promising that the cases were so mild.

“I have not yet heard of anybody who has been vaccinated that has gotten sick or died of Covid yet. And given all the cases that are potentially there, I think that’s a good sign.”

He said a good way to imagine a vaccine is to think of it as a shield.

“It only stops 95% of the arrows. So if a thousand arrows get shot at one person, it’s not going to stop them all. But if arrows are much fewer, it will stop them all, with an occasional exception that might get through. But even the ones that get through are slowed down by the shield and then maybe they’ll just prick the person as opposed to skewering them.”

Herd immunity is a good way to make the shield more effective, said Picker.

“When the pandemic is raging, a lone vaccinated person in a sea of a raging pandemic there’s still a chance that you could get infected. Whereas, once more people get vaccinated and the number of cases go down. Then that risk goes away really quickly. Then we only have a couple arrows shot at you and you can block 95 of them out of a hundred, then you’re probably going to be good.”

Picker also said that efficacy rates are really just based on the studies done on the vaccines and that each study has its own methodology. 

“Determining efficacy is sort of empirical, and it’s hard to compare efficacy because they do their studies differently. The number of efficacy sort of depends on what you define as efficacy, when you count it and what you’re counting. Are you counting deaths? Are you counting sick people? Are you counting people that had the virus but no symptoms? There’s a lot of different ways to count it.” 

But he said that it is promising that the two mRNA vaccines had such high efficacy rates.

“But it is interesting that the two mRNA vaccines both worked, the trials were similar and they both worked to a similar high degree. Some of the other vaccines coming through, like the Johnson & Johnson vaccine, look like they’re lower efficacy. But to me that just remains to be seen if that’s just a matter of how it looked in their study. And I suspect when it’s all said and done, the efficacy of that vaccine will also be high.”

Picker said that we can’t afford to wait and choose based on the type or efficacy of the vaccine.

“We don’t know enough about any of them for any of us to be sitting there and choosing them. My advice to anyone is to get whatever vaccine that you’re capable of getting as soon as possible, of course once they have the Emergency Use Authorization, and leave it at that. I think in the end, we’ll look back two years from now and say ‘ok well this one was better’ or ‘this one was better,’ but we really don’t have a good idea now of how to compare them. But the two EUA vaccines, and the Johnson and Johnson next week is going to the FDA, is meeting the criteria for use. And all of these vaccines are much, much, much better than no vaccine.”