Medical Technology

Pre-omicron Study – Vaccines Offer 8 Months of Protection against COVID Hospitalization

(Reuters Health) – A North Carolina study of the waning effectiveness of the three COVID-19 vaccines given in the United States shows that although protection against illness from the novel coronavirus fades after six to eight months, protection against hospitalization and death remains high, especially with the two messenger RNA vaccines.

Among early-2021 recipients of the Pfizer and Moderna mRNA vaccines, “effectiveness decreased by approximately 15 and 10 percentage points, respectively, from mid-June to mid-July,” said a team led by Dan-Yu Lin of the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill.

They blame both declining immunity and the emergence of the more-transmissible Delta variant of the virus.

“Our results suggest that (1) booster shots should be given to the Pfizer vaccine recipients earlier than the Moderna vaccine recipients, (2) the recipient of the Johnson &Johnson vaccine should take the second dose around one month (rather than 2 months) after the initial injection; and (3) booster shots are more important for older adults than younger adults and children” because older adults lose their immunity faster, Dr. Lin told Reuters Health in an email.

The data, gathered through September 8, 2021, predate the emergence of the Omicron variant currently sweeping the world.

Asked about the relevance of the study to the current phase of the pandemic, Dr. Lin said that because “our study found that vaccine effectiveness against infection is high but wanes over time and that vaccine effectiveness against hospitalization and death is durably high . . . the best way to fight against the omicron variant is to vaccinate the unvaccinated and booster those with weak immunity.”

The study, published online by the New England Journal of Medicine, estimated long-term effectiveness using records from the 10.6 million people in North Carolina.

The effect of booster shots was not assessed.

Recipients of the Moderna vaccine fared the best, but the advantage over Pfizer was not dramatic.

Moderna’s effectiveness against illness peaked at 95.9% at 2 months, and fell to 80.3% after 7 months. Protection against hospitalization peaked at 97.2% at 2 months, and was still above 94% by month 8. Protection against death peaked at 98.6% at month 2, and was at 96% eight months after the first shot.

The Pfizer vaccine showed a similar pattern but a slightly steeper decline over time.

Pfizer’s protection peaked at 94.5% during the second month and dropped to about 80% two months earlier than it did among Moderna recipients. By the eighth month, the effectiveness for protecting against illness was at 67.8%.

After two months, Pfizer reduced risk of hospitalization by 96.4%. By the eighth month, it was blocking 92.4% of hospitalizations.

Deaths were reduced by 98% at two months. After eight months, effectiveness against death was 95.5%, essentially the same as with the Moderna vaccine.

The one-dose Johnson & Johnson vaccine was only assessed for six months because its introduction came later in the year.

Its effectiveness against illness was 74.8% in the first month and declined to 64% by the sixth month. It’s peak effectiveness against hospitalization came in the second month at 85.8%. That had declined to 81.7% by month 6, according to the data.

The Johnson & Johnson product was providing protection 85.9% protection against death by the third month, and 71.2% by the sixth month.

People over 65 had a lesser degree of protection against hospitalization and death than younger vaccine recipients, but the difference was particularly pronounced among folks who received the Johnson & Johnson jab.

After 8 months, hospitalizations were reduced about 94% in Pfizer recipients under 65, but for those 65 and older, effectiveness was 90%.

Moderna’s vaccine had slightly better numbers, with an effectiveness of about 97% in adults under 65 and 93% among seniors.

Six months after getting the Johnson & Johnson shot, the effectiveness was 91% for adults under 50, 86% for ages 50 to 64, and 72% for people 65 and older.

The effectiveness of all three vaccines for preventing death was over 90% six months after inoculation.

“The fact that COVID-19 vaccines, especially the two mRNA vaccines, are so effective and durable, especially against hospitalization and death, should quell vaccine hesitancy,” said Dr. Lin, a professor of biostatistics at UNC. “It is ironic that the United States, which developed and produced these miracle vaccines, has the lowest vaccination rates among the world’s wealthiest democracies.”

When it comes to making a choice between the vaccines, “J&J vaccine is clearly less effective than the two mRNA vaccines,” he said. “There is no practical advantage of taking the J&J vaccine if one has to take a second shot 1-2 months after the first anyway.”

“We don’t know the effectiveness of a two-dose J&J regimen, but it is unlikely to be higher than that of the two-dose regimen of the Pfizer or Moderna vaccine,” he added. “Since the two mRNA vaccines are highly effective and widely available, there is no strong reason to take the J&J vaccine.”

SOURCE: The New England Journal of Medicine, online January 12, 2022.

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