More vaccination questions and answers

In the May 22 issue of WORLD, we ran a coronavirus vaccine Q&A with Dr. Charles Horton and invited readers to submit their own questions. Here’s a new installment:

You wrote in an earlier article that mask wearing led to the lightest flu year in recent history. If masks are effective against respiratory viruses, why did we have 32.5 million COVID-19 cases in the United States and more than 578,000 deaths? Do masks only work on the flu?

Multiple factors play into this. The first is that the COVID-19 virus is more contagious than the flu. Looking at its R₀ (“R naught”) value—the number of people an infected patient is expected to infect—this chart shows the H1N1 flu has an R₀ of around 1.4. That means each person who had the flu gave it to one, or perhaps two, others. For COVID-19, each person passes it to an average of 1.5 to 3.5 people. The R₀ range represents the effects of societal responses: Only with aggressive management were we able to get COVID-19’s R₀ near that of the flu.

Second, while asymptomatic transmission of flu isn’t impossible, it’s not nearly the factor that it is with COVID-19. This matters because we as a society made a healthy change in 2020: We decided that we wouldn’t go to work (or shopping, or socializing) while sick. This interfered with flu transmission far more than COVID-19 transmission.

Is it safe for my 9-month-old baby to play with his young cousins who go to daycare or school? What rules should we put in place when meeting unvaccinated relatives for the first time?

Go for it! Remember, children almost always fare much better than older adults if they’re exposed to the coronavirus. Once we understood this, restrictions on children had more to do with concerns that they’d transmit the virus to grown-ups who might fare poorly. Nowadays, the vaccine is widely available and confers good protection for adults.

We can consider the question of unvaccinated relatives from a few angles. Assuming you’re fully vaccinated, the chance of you coming to harm is very low, and the chance of you bringing the virus to your relatives is also very low. Very young children, like your 9-month-old, don’t seem to spread COVID-19 very well—but the question of interacting with young cousins who go to daycare and then visiting unvaccinated relatives does depend on each family’s level of risk tolerance.

Will the coronavirus vaccines based on mRNA change your DNA?

No. Part of the public confusion on this issue is that RNA sounds a lot like DNA. The full version sounds even more similar: DNA is deoxyribonucleic acid, whereas RNA just lops off the “deoxy” prefix. But the difference is huge: DNA is the master copy of your body’s genetic code. RNA is an intermediate step in making proteins from DNA instructions. It serves as a messenger (and yes, that’s the “m” in “mRNA”).

Are there other concerns about mRNA vaccines? Could it weaken the immune system and its effectiveness in fighting against future viruses?

Most of the concerns I’ve seen stem from one of two issues. The first is that mRNA vaccines haven’t been widely deployed before. The technology has existed, but this is its first moment on the world stage. And the second is that we don’t have long-term safety data. (One might fairly point out here that we also don’t know the long-term effects of COVID-19 infection.)

It is not impossible for vaccines to alter the immune response in undesirable ways, but those problems are better understood now: A 1967 incident with vaccines against a childhood respiratory bug (called respiratory syncytial virus, or RSV) brought those problems to light, and vaccine developers now watch for similar problems in pre-market and post-market testing.

A few scientists have hypothesized that the vaccines could weaken immunity, either against COVID-19 or against other pathogens. Their proven effectiveness against COVID-19 disproves the former idea, and there is as yet no evidence of the latter.

How can you trust a vaccine when we do not yet know what its long-term effects are?

I’ll say here what I say to my patients before a procedure: The chance of things going badly wrong is never zero with any human endeavor, but it can be very low. If by “trust” we mean absolute certainty that nothing will go wrong with anyone taking it, we’re setting an impossibly high bar: We deal with side effects from antibiotics frequently, but that wouldn’t make us withhold them from patients who need them.

This isn’t at all the same as saying the vaccines are untested, and we’ve learned a lot about the vaccines both from the phase 3 studies (the large studies done before the Food and Drug Administration’s emergency use authorization) and from the phase 4 studies (the post-marketing surveillance). Remember, the phase 3 studies started last summer: The first study patients who received those vaccines are coming up on their first anniversary of their shots. None of this completely excludes the possibility of problems cropping up later, but it makes it highly unlikely as time passes.

Are there many adverse reactions to the vaccines that aren’t being reported?

As with many vicious rumors, this one contains a kernel of truth, but that kernel is being twisted to produce a very inaccurate conclusion. Much of the concern has arisen when people misinterpret data from VAERS, or the Vaccine Adverse Event Reporting System. This system, which collects everything people submit to avoid missing important trends, is only as good as its submissions. (One researcher famously demonstrated this by filing, and later withdrawing, a report that a vaccine had caused him to turn into the Incredible Hulk.)

Keep in mind that the vaccine doesn’t provide much protection until a few weeks after the first dose and that VAERS collected submissions on millions of frail elderly people during a pandemic. A COVID-19 death one week after the vaccine could well be filed with VAERS as “death after the vaccine.” It would be a death, and it would be after the vaccine. But it’s not a death from the vaccine.

This nuance has led to one persistent theme in internet disinformation, holding that the FDA is somehow hiding large numbers of vaccine-related deaths. But supposing that this was the case, clearly people would be missing with relatives demanding answers. We’re not seeing this.

How do viral mutations and adaptations play into the picture?

The ongoing problem of a mutating coronavirus has underlined how wisely the United States acted in stockpiling vaccines early as countries around the world continue to face fresh outbreaks. Mutations spread more easily between unvaccinated people, making it harder for countries that fell behind in the fight to catch up.

The mRNA vaccines control the coronavirus variants we’ve seen so far, too. The variants may not be quite as susceptible as “original” COVID-19, but they don’t seem able to dodge the antibodies from the vaccine entirely.

What about people who cannot be vaccinated due to allergic reactions to medications and foods? Those who have inflammatory responses are advised not to get the vaccine.

According to Yale’s online COVID-19 resource pages, people who have experienced severe (anaphylactic) reactions to any component of a given vaccine shouldn’t get that vaccine, and people who’ve had an anaphylactic reaction to something given by injection should talk with their doctors first. Most would still be candidates for the vaccine after that talk because the types of medication most associated with anaphylaxis (such as antibiotics and potent muscle relaxants used during general anesthesia) aren’t found in the vaccine.

For those few people who truly can’t receive the vaccine, the path I’d recommend involves masks, distancing, and encouraging everyone around them to get their own vaccine to protect those who can’t.

Why aren’t the Centers for Disease Control and Prevention and medical providers including those who have had COVID-19 and have a positive IgG test for antibodies to be in the same category as the fully vaccinated?

The CDC had initially appeared reluctant to do that, largely due to concerns about how long antibodies remain. Reassuring evidence has recently come in from two large, well-run British studies. Yet those two studies took place before viral variants became commonplace in the United Kingdom, so questions remain. With that said, I do think that as time passes, vaccinated people and people who have recovered from COVID-19 will likely come to be seen as having a similar risk of symptomatic COVID-19 disease.

—A version of this article appears in the June 26 print edition.