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Vaccines: Go Get ‘em
Don Mosier, MD, PhD

In-car vaccination at Petco Park. Photo Liz Sloan.

Governor Newsom announced on January 12th that anyone over 65 could get the COVID-19 vaccine. That is good news. Both Scripps Health and UCSD have begun to immunize older clients although appointments are filling up fast. Unfortunately, immunization of health care workers and nursing home residents is well behind schedule and vaccine supplies are running short, so the timing of exactly when all Del Mar seniors can get both vaccine doses remains uncertain.

Let’s imagine that you are lucky, whatever age you are, and get your two doses of vaccine before the end of February and you are among the 95% projected to develop protective immunity. Can you resume normal life with friends and hug your grandkids? The short answer is no. First, you need to wait at least 3 weeks after the second dose for the peak immune response to develop. We still need to understand more about how robust this immune response is at that point. The trials that allowed the Pfizer and Moderna vaccines to be distributed proved that two doses of vaccine prevented 95% of symptomatic COVID-19 disease, which is very impressive and an important reason to get the vaccine. It remains to be determined if the vaccines prevented infection with the virus or cleared the virus infection before it could cause disease. Because up to 50% of COVID-19 infections are asymptomatic, it is possible that a vaccinated individual could become infected and potentially transmit the virus before a robust immune response limited the infection. Most vaccines work by priming the immune system to rapidly respond to a virus infection, but a very robust immunity that prevents any virus replication is uncommon. Also, you could be unlucky and be in the 5% with poor vaccine responses.

That means that you need to continue to wear a mask and practice social distancing even if you have received the COVID vaccine. Save those grandkid hugs for later, when everyone has been vaccinated and virus infections are very rare.

Three new variants of the COVID-19 virus have emerged in recent weeks. One arose in the United Kingdom and has been detected in San Diego County. The second arose in Brazil and appears responsible for a second wave of infections in Manaus. A third is prevalent in Northern California. Each appears more infectious than the predominant strain in the US, and the genetic sequences indicate changes in the viral spike protein that is critical for virus entry into human cells. Although the current vaccines seem to be effective against the new variants, the results from Brazil are worrying because some people infected in the first wave last summer remain susceptible to infection by the new variant. We don’t know whether immunity from the first infection was short-lived or the new variant was poorly recognized by the immune system, or both. With millions of people infected worldwide and the coronavirus mutating faster than expected, we will have to keep a vigilant watch for mutations that both increase transmission and escape the protection conferred by the current vaccines. But stay tuned, because a second round of vaccines against emerging COVID-19 variants may be needed in the coming years.

In the meantime, it is urgent that as many people as possible get the COVID-19 vaccines as soon as possible. The more people that are infected, the more likely a dangerous mutation is to emerge. Let’s slow this pandemic before that happens.

 

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